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Biomedical subjects

K Lohmann

Publications and source records attributed to K Lohmann.

26 records · Page 2Linked to original sources
PubMed1989

[Behavior and pathogenicity of larva of Toxocara canis Werner 1782 (Anisakidae) in the mouse].

To evaluate the interdependence between pathological changes and the level of infection the behaviour of Toxocara canis larvae in the host, the course of the disease as well as quality and quantity of histological changes were investigated after experimental infection with 1,000, 500, 250, and 125 larvae respectively. The main places where the larvae of Toxocara canis were found at any time after infection were musculature and brain. Regardless of the level of infection the absolute and relative number of larvae in the brain increased linearly, and parallel decreased in musculature. After the 60th day post infection the mice infected with 1,000 larvae showed compulsive movements, disturbance of equilibrium and paralysis of the hindlegs. The mice infected with 500 larvae showed similar symptoms 30 to 40 days later. Mice with weaker infections only showed slight disturbances of the general condition at the end of the trials. In the brain of all animals infected with larvae of Toxocara canis inflammatory reactions were found. Severe destructive changes in the nervous substance together with clinical symptoms were seen only in higher infected mice.

Animals↗
PubMed1986

Length polymorphism in rDNA indicates somatic alterations in the genome of Triturus vulgaris.

We have analyzed the EcoRI restriction pattern of ribosomal genes (rDNA) isolated from several organs of single individuals of the newt Triturus vulgaris by Southern blotting and hybridization with corresponding Xenopus probes (r11 and r12). Using length polymorphism of rDNA spacers as a molecular marker, it became evident that in individual newts the pattern of ribosomal genes is not always constant but varies between different tissues of the same animal suggesting the occurrence of genome alterations during ontogenesis.

Animals↗
PubMed1985

Are there insertions in the ribosomal DNA of vertebrates?

We have analysed the Eco RI restriction pattern of rDNA of the newt Triturus vulgaris and of some other amphibian species by Southern blotting and hybridization with nick-translated Xenopus rDNA prepared from the recombinant plasmids pXlr11 and pXlr12 (21). After hybridization with r11, the 28S coding fragments become visible in two bands, a prominent one of 5.3 kb and a weak band of 5.9 kb representing about 8% of the 28S genes. The evidence obtained so far by additional digestions with Bam HI and Bgl II indicates that in this species and in Triturus helveticus the coding regions of the 5.9 kb fragments are interrupted by an insertion 0.6 kb in length located in a 1.6 kb Bgl II fragment at the 3' end of the Eco RI fragment, which we believe to be the first described in a vertebrate.

Animals↗
PubMed1980

Qualitative changes in DNA indicating differential DNA replication during early embryogenesis of the newt Triturus vulgaris.

During gastrulation of the newt Triturus vulgaris considerable changes in the melting behaviour and in the CsCl density gradient pattern of DNA occur. The melting curves of DNAs from mid to late gastrulae (stages 11b-12c) deviate from the regular shape. Whereas the Tm values are identical in the stages 11a (early gastrula) and 15 (early neurula), and correspond to the standard DNA (stage 36 = tailbud), a significant rise of Tm (0.8-1.2 degrees C) has been recorded in the stages 12a/b (yolk plug). The differences in melting behaviour become visible by the deviation of the curves above Tm. These deviations from the normal sigmoidal shape are caused by the fact that a portion of DNA melts at higher temperatures than usual. Therefore the thermal denaturation of DNA is completed at approximately 3-4 degrees C later than in standard DNA. Both the derivative curves and the plots on normal probability paper demonstrate a heterogeneity of DNA in the stages 11b-12c which indicates the presence of an additional GC-rich satellite fraction. These findings are confirmed by CsCl density gradient studies. Thus, in the stages 12a/b a slight shoulder on the heavy side of the gradients occurs, being absent in the other stages. From these facts we have to conclude that there is a stage-dependent multiplication and elimination of GC-rich sequences.

Animals↗
PubMed1979

Tissue-specific changes in nuclear RNA content during early development of Triturus vulgaris.

During early development of Triturus vulgaris, as a measure for nuclear activity in neuroectoderm, mesoderm and endoderm, nuclear RNA content was determined by cytochemical methods. In the first stages of gastrulation, that is to say during the early phase of neural induction, the RNA content of the inducing system is considerably higher than in the reacting system. Then, with a phase-shift of about 10 h, the RNA content of the neuroectoderm increases quickly also. In the following stages the nuclear RNA content of both regions is reduced. A second continuous increase in the RNA amount coincides with the formation of the neural tube. In the mesoderm, enhancement of RNA content correlates with cytodifferentiation of the chorda. In all stages the RNA content of the endoderm is higher than in the other tissues and it becomes successively diminished from the early gastrula to the tailbud stage.

Animals↗
PubMed1977

Changes in the thermal denaturation profiles of DNA from different developmental stages of the newt Triturus vulgaris.

The melting profiles of DNA samples from the early gastrula and early neurula of Triturus vulgaris are essentially the same, whereas DNA from mid to late gastrula possesses higher Tm values and shows a deviation from the regular sigmoidal shape at temperatures above Tm. The plot on normal probability paper indicates a second DNA fraction which melts at higher temperatures and, consequently, it has a higher GC-content than the bulk of DNA. These facts confirm our idea that differential DNA replication occurs during gastrulation.

Animals↗
PubMed1976

Cytochemical evidence for stage-specific changes of nuclear RNA and nonhistone protein content during early development of Triturus vulgaris.

During early embryogenesis of Triturus vulgaris, RNA and nonhistone protein contents of neuroectoderm nuclei change with stage specifically. Maximum values were found in the late gastrula after embryonic induction, and in the late neurula with the formation of the neural tube. The stage-specific increases of RNA and nonhistone protein are correlated with a preceding increase of Feulgen-DNA content.

Animals↗