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Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 775 records · Page 43Linked to original sources
PubMed1981

[Age related alterations of motor behavior and release of dopaminergic supersensitivity in rats].

Rats aged greater than or equal to 18 months show, aside from clearly diminished motor parameters (exploratory behavior, resting activity, nocturnal activity profile, rotation behavior), after intracerebral dopamine injection a considerably lower apomorphine hypermotility than young animals. The characteristic alteration of activity occurring in young rats during and following chronic administration of haloperidol (1 mg/kg . day, s.c. for 21 days) as an expression of developing dopaminergic supersensitivity does not appear in older animals. Repeated application of amphetamine (2 X 2 mg/kg daily) caused a significant increase in hypermotility. The results are interpreted as the consequence of a age-related reduction of the activity of central-dopaminergic transmission systems and are discussed with regard to possible differences in the realization of agonist- or antagonist-induced supersensitivity.

Age Factors↗
PubMed1981

Effects of nootropic drugs on dopaminergic systems in the CNS.

The effect of 3 nootropic drugs, meclofenoxat (MEC), piracetam (PIR) and orotic acid (methylglucamine orotate, MGO), on locomotor activity and on rotational behavior after intracerebral injection of dopamine was tested in female Wistar rats. Whereas MGO-pretreatment increased the dopaminergic supersensitivity following repeated haloperidol in both behavioral tests, the other nootropics were without influence on intensity and duration of supersensitivity. Stimulating and sedative action of apomorphine on locomotion (following 2 mg/kg and 40 micrograms/kg apomorphine sc, respectively) was found to be unchanged after single doses of nootropics (300 mg/kg PIR or MEC, 225 mg/kg MGO, 30 min before apomorphine). Preceding systemic application of nootropics did not change the rotational behavior following application of dopamine (200 micrograms/2 microliters) into nucleus accumbens or nucleus caudatoputamen. The results show that nootropic drugs are without influence on spontaneous and dopaminergically stimulated locomotor activity but in contrast to PIR and MEC, MGO is able to facilitate the dopaminergic supersensitivity.

Animals↗
PubMed1981

[Improvement of the radiological protection in the interstitial radiotherapy with radiogold seeds (author's transl)].

In spite of all its advantages, the interstitial therapy with radiogold seeds has the disadvantage to expose the staff to a higher radiation loading than other nuclides and therapy methods. For the application of an implantation canula with linear arrangement of the radiogold seeds before the ejector (according to Hellriegel), the authors propose a simple device which can also be self-fabricated, to protect from gamma radiation during transport and laying down of the set ready for use. Construction and application are described. At a distance of 10 cm from the lead container, the radiation dose amounts to 0.3 mR/h per 1 mCi (37 MBq) of the activity of the seeds. The use of interstitial radiotherapy is also possible in small departments. The authors inform their practical experiences gained during the treatment of 26 patients.

Brachytherapy↗
PubMed1980

Primary structure and binding properties of iodinated derivatives of alpha-bungarotoxin.

Iodination of alpha-bungarotoxin (alpha BuTx) gives rise to two products, mono- and diiodo-alpha BuTx. A combination of enzymatic digestion and Edman degradation revealed that the iodinated derivatives contain label in residue Tyr 54 exclusively. This labeling pattern is reminiscent of the reactivity toward iodination of "short" neurotoxins. The binding properties of the two derivatives were compared. At 20 degrees C, in 10 mM sodium phosphate, pH 7.4, the association of mono-125I-alpha BuTx to detergent-solubilized Torpedo californica electroplax acetylcholine receptor is characterized by a rate constant of 5.2 X 10(6) M-1 s-1, which is indistinguishable from the on-rate constant of the native toxin. Introduction of the second iodine atom reduces the association rate constant to 1.7 X 10(6) M-1 s-1. The diiodo derivative was also found to bind more slowly than the monoiodinated toxin by factors of 2.6 and 2.5 to partially purified preparations of acetylcholine receptor from denervated chick muscle and of toxin receptor from chick brain, respectively. No difference in dissociation kinetics was observed; both derivatives bind irreversibly to electric tissue and muscle acetylcholine receptor and dissociate from the neuronal receptor with an off-rate constant of 5.9 X 10(-5) s-1. In muscle, two sets of binding sites are kinetically distinguishable as originally observed by Brockes and Hall (Brockes, J. P., and Hall, Z. W. (1975) Biochemistry 14, 2092-2099). Di-125I-alpha BuTx binds more slowly to each site than mono-125I-alpha BuTx by factors of 2.0 and 3.7, respectively.

Amino Acid Sequence↗
PubMed1980

Effects of preceding sensibilization by reserpine and haloperidol on toxicity of dopaminergic agonists.

The effect of dopaminergic supersensitivity induced by repeated administration of neuroleptics on the toxicity of amphetamine in mice has been examined. As well as haloperidol, reserpine pretreatment increased the toxicity of amphetamine. Combined pretreatment did not cause a further increase of mortality following amphetamine. Dose response curves were not parallel, which might indicate different causes of death in naive and sensitized mice. Pretreatment with haloperidol did not change the toxicity of reserpine. The potentiating effects of neuroleptics on amphetamine toxicity may be connected with their ability to induce supersensitivity to dopaminergic agonists.

Amphetamine↗
PubMed1980

Detection of demyelinated plaques with xenon-enhanced computed tomography.

Studies of xenon-enhanced CT for detecting cerebral demyelination have produced conflicting results. Therefore, we studied the effect of xenon inhalation on the CT appearance of five demyelinated plaques. The plaques and the surrounding white matter increased commensurately in attenuation during xenon inhalation. Therefore, xenon enhancement does not generally increase the sensitivity of CT for detecting cerebral demyelination.

Brain↗
PubMed1980

High frequencies of antigen-specific hybridomas: dependence on immunization parameters and prediction by spleen cell analysis.

Hybridomas producing antibodies against soluble antigens have in most cases been difficult to establish. After fusion of myeloma cells with spleen cells obtained from mice immunized with a soluble protein, hybridomas secreting specific antibodies have been observed to occur very rarely among non-specific hybridomas. We found that the frequency of specific hybridomas correlates directly with the increase over background of the frequency of blast and/or plasma cells in the spleen (measured by cell size analysis) after antigenic stimulation. High yields of specific hybridomas were obtained simply by following a novel immunization technique consisting of several conventional preimmunization courses followed by 4 very high doses of antigen in saline on each of the last 4 days before fusion.

Animals↗
PubMed1980

Clinical cerebral blood flow measurement with inhaled xenon and CT.

Cerebral blood flow measurement has not yet been attempted with xenon and CT in patients. Xenon washout was studied in three patients receiving subanesthetic concentrations of xenon. Cerebral enhancement after 30%--50% inhaled xenon was demonstrated without serious side effects. Clinical cerebral blood flow measurements with xenon and CT may be feasible.

Cerebrovascular Circulation↗
PubMed1980

[Aetiology and importance of viral diseases of the respiratory tract (author's transl)].

After discussion of the epidemiological situation of acute respiratory diseases and their economic consequences, and after a survey of clinical signs and symptoms, a review is given of the most important viral agents causing such diseases. That are influenza, parainfluenza, respiratory syncytial, adeno, corona, REO, and rhino viruses, which are prevalent in the respiratory tract. Viruses predominantly localized outside of the respiratory tract as well as bacteria and bacteria-like microorganisms are only shortly mentioned. Most weight is given to virological problems (morphology, antigenic structure), to pathogenic property and importance of viruses causing acute respiratory diseases.

Adenoviruses, Human↗