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Biomedical subjects

L Wieslander

Publications and source records attributed to L Wieslander.

62 records · Page 4Linked to original sources
PubMed1975

The location of repeated DNA sequences in the chromosomes of Chironomus tentans.

Polytene chromosomes of Chironomus tentans were hybridized in situ with in vivo labelled nuclear and chromosomal RNA. Nuclear RNA formed hybrids preferentially in five distinct regions considered to contain clustered, repeated DNA sequences. These are the two nucleolar organizer regions, Balbiani ring 1 and 2, and the 5 S RNA genes in region 2A of chromosome II, which together comprised almost 70% of the total number of grains over the complement. The remaining grains were diffusely distributed over the chromosomes. There was a significant difference in the distribution of grains when RNA from different chromosomes was used for hybridization. Chromosome I RNA hybridized preferentially with chromosome I, and chromosome II+III RNA preferentially with chromosome II+III. Some regions within the chromosomes hybridized significantly more chromosomal RNA than other regions. A considerable cross-hybridization of RNA from one particular type of chromosome with the other chromosomes was also found. It is concluded that repeated DNA sequences which hybridize with heterogeneous chromosomal RNA in C. tentans are widely dispersed in the genome. Some of these sequences have a delimited localization, others are dispersed, and some sequences which are transcribed in one particular chromosome are present also in the other chromosomes.

Amino Acid Sequence↗
PubMed1975

Localization of 5 S RNA genes in Chirnomus tentans.

The genes for 5 S RNA in Chironomus tentans have been located to region 2A of chromosome II by cytological hybridization. RNA from individual chromosomes, nuclear sap and nucleoli of salivary gland cells hybridized with the identified 5 S RNA genes in region 2A of chromosome II. The results suggest a common origin of 5 S RNA in these different nuclear compartments.

Animals↗
PubMed1975

The presence of 5 S RNA genes in two consecutive chromosome bands in Chironomus tentans.

It has earlier been shown by in situ hybridization that the 5 S RNA genes are located in region 2A of chromosome II in Chironomus tentans [1]. In the present study the resolution in this chromosome region could be considerably improved by using the inversion 1 A/9C of chromosome II, which carries region 2A, not in the usual position close to one end of chromosome II, but in the middle of the chromosome. It was then revealed that electrophoretically isolated 5 S RNA hybridized in situ with two adjacent bands in the region 2A. It was also observed that in heterozygotes harbouring one normal chromosome II and one with the inversion 1 A/9C, there is a close physical contact between the bands containing the 5 S RNA genes and the nucleolar organizer region.

Animals↗
PubMed1975

Early or late cervical traction therapy of Class II malocclusion in the mixed dentition.

It was the purpose of this investigation to evaluate the effect of cervical traction in Class II malocclusions in which treatment was started either early or late in the mixed dentition. Evaluation of the data indicated that the amount and direction of growth were of the greatest importance for effective treatment. Vertical growth appeared to be of particular importance and correlated to the anteroposterior improvement of the relationship between the maxilla and the mandible. Cervical traction, as advocated in this study, was more favorable in the early mixed dentition. A greater amount of growth and a subsequent increased reduction in the ANB angle was recorded during this period. The effect of treatment upon the maxilla, as revealed in posterior movement of the maxillary molar and the pterygomaxillary fissure, was more evident in early treatment. Great individual variability was observed, but in cases in which there was a severe discrepancy in the relationship between the maxilla and the mandible treatment in the early mixed dentition may be essential.

Cephalometry↗
PubMed1972

In situ demonstration of DNA hybridizing with chromosomal and nuclear sap RNA in Chironomus tentans.

Cytological hybridization combined with microdissection of Chironomus tentans salivary gland cells was used to locate DNA complementary to newly synthesized RNA from chromosomes and nuclear sap and from a single chromosomal puff, the Balbiani ring 2 (BR 2). Salivary glands were incubated with tritiated nucleosides. The labeled RNA was extracted from microdissected nuclei and hybridized to denatured squash preparations of salivary gland cells under conditions which primarily allow repeated sequences to interact. The bound RNA, resistant to ribonuclease treatment, was detected radioautographically. It was found that BR 2 RNA hybridizes specifically with the BR 2 region of chromosome IV. Nuclear sap RNA was fractionated into high and low molecular-weight RNA; the former hybridizes with the BR 2 region of chromosome IV, the latter in a diffuse distribution over the whole chromosome set. RNA from chromosome I hybridizes diffusely with all chromosomes. Nucleolar RNA hybridizes specifically with the nucleolar organizers, contained in chromosomes II and III. It is concluded that the BR 2 region of chromosome IV contains repeated DNA sequences and that nuclear sap contains BR 2 RNA.

Animals↗