Search PubMed⌕ Search

Biomedical subjects

L Lindahl

Publications and source records attributed to L Lindahl.

At least 73 records · Page 4Linked to original sources
PubMed1980

Masticatory muscle function in patients treated for condylar fractures of the mandible.

The activity of the temporal and masseter muscles and of the upper lip was examined by electromyography in five adults and in five children who had sustained uni- and bilateral fractures of the mandibular condyle. Electromyographic recordings were done in the postural position of the mandible, during maximal bite in the intercuspal and retruded mandibular positions, during chewing and swallowing of peanuts and during swallowing of water. In the children, who were examined on three occasions after the trauma, a reduced muscle activity was found shortly after the trauma, but it had normalized at follow-up examination 1 year after the injury. The adults, who were examined 4-6 years after the trauma, had, in general, normal muscle function. In subjects with a unilateral fracture, no difference in muscle activity was found between the two sides. An enlarged distance between the retruded and intercuspal positions of the mandible did not, in these subjects, seem to influence the muscle activity during the functions studied.

Adolescent↗
PubMed1979

Operon-specific regulation of ribosomal protein synthesis in Escherichia coli.

We have cloned a DNA fragment harboring the genes for ribosomal proteins L2, L4, and L23 on a plasmid vector that contains a lac operator and promoter. The cloned ribosomal protein genes are now under the control of lacOP. Addition of a lac inducer to these cells results in a specific 5- to 10-fold increase in the synthesis of the proteins corresponding to the cloned genes. Within 10 min of this induction, the synthesis of ribosomal proteins S3, S19, L3, L16, L22, and L29 stops almost completely. The genes for all these proteins reside in the same chromosomal operon as L2, L4, and L23. We have seen no dramatic effect on the synthesis of any other ribosomal proteins. Thus, the induction of L2, L4, and L23 results in a specific and rapid decrease in the expression of all (or almost all) genes in their own transcription unit.

Bacterial Proteins↗
PubMed1978

Some rRNA operons in E. coli have tRNA genes at their distal ends.

We have previously isolated seven rRNA operons on plasmids or lambda transducing phages and identified various tRNAs encoded by these operons. Each of the seven operons has one of two different spacer tRNA gene arrangements between the genes for 16S and 23S rRNA: either tRNAGlu2 or both tRNAIle1 and tRNAAla1B genes. In addition, various tRNA genes are located at or near the distal ends of rRNA operons. In particular, genes for tRNATrp and tRNAAsp1 are located at the distal end of rrnC at 83 min on the E. coli chromosome. Experiments with various hybrid plasmids, some of which lack the rRNA promoter, have now demonstrated that this promoter is necessary for expression of the distal tRNA genes. Rifampicin run-out experiments have also provided evidence that the tRNATrp gene is located farther from its promoter than the spacer tRNA gene or the 5S RNA gene. These results confirm the localization of genes for tRNATrp and tRNAAsp1 at the distal end of rrnC and strongly suggest that they are co-transcribed with the genes for 16S, tRNAGlu2, 23S and 5S RNA. Other such distal tRNAs have been identified, and it is suggested that they too are part of rRNA operons.

Chromosome Mapping↗
PubMed1978

Integrated prosthetic and surgical treatment of malignant tumours of the maxilla. A new acrylic plate device.

Surgery for malignant tumours involving the palate often leads to postoperative problems for the patient. Most commonly a stent or a tampon is used to fill the resection cavity. Both materials have disadvantages, however. To overcome these we have since 1972 used a preoperatively made acrylic plate to separate the oral cavity from the resection cavity in 20 patients. This plate is fixed to the mucosa or to the remaining teeth by sutures and is left in place for 10-14 days postoperatively.

Acrylic Resins↗
PubMed1977

Condylar fractures of the mandible. IV. Function of the masticatory system.

The masticatory system was followed-up with respect to symptoms of dysfunction such as restricted mandibular movements, tenderness, and clicking from muscles and joints at predetermined times after condylar fractures of the mandible in 24 children, 17 teenagers, and 26 adults. Two years after the trauma, the initially reduced (less than 40 mm) maximal opening became normal (larger than or equal to 40 mm) in all but one individual. Asymmetry of mandibular movements, such as deviation at maximal opening and differences between fractured and nonfractured side in maximal lacterotrusion and protrusion, usually disappeared within 2 years in children, while it persisted or became aggravated in adults. Persistent symtoms from the joints and muscles, such as clicking and tenderness, were rare in children and frequent in adults.

Adolescent↗
PubMed1977

Condylar fractures of the mandible. II. a radiographic study of remodeling processes in the temporomandibular joint.

Remodeling processes in 76 temporomandibular joints were studied on radiographs from 67 individuals sustaining condylar fractures. The indivuduals were ranged into four age groups: 3-11, 12-15, 16-19, and larger than or equal to 20 years of age at the time of fracture. The radiographic examinations were to be performed at the time of the trauma and 3, 6, 12, 24 and 36-48 months after the injury. In the age group 3-11 there was a complete return to normal skeletal relations in 20 of the 27 joints. Joints in teenagers (12-19) did not become normal to the same extent and in adults only minor remodeling was observed. In children the remodeling of the condylar process was extensive but indistinctly outlined. With increasing age there was a shift towards a more distinct apposition of bone on the posterior part of the condylar head visualized as a double contour. This contour first appeared in the late teens. In adults the remodeling processes seemed only to be part of the functional adjustment. Thus, the remodeling processes of the condylar process in a clinical sense may be looked upon as restitutional in children and adjusting or functional in adults. As regards the articular fossa, in children the remodeling processes were first observed as a double contour, of which the new one became more and more distinct, while the original roof gradually disappeared. The final results was a flattened fossa. In adults, a sclerosis of the roof of the fossa was found.

Adolescent↗
PubMed1977

Condylar fractures of the mandible. III. positional changes of the chin.

Positional changes of the chin (symphysion = sy) following unilateral condylar fractures of the mandible were studied in 21 children and 20 adults by means of repeated radiographic examinations. On each occasion and for each individual the actual position of the sy was related to an estimated normal position. In those children in whom the remodeling processes in the temporomandibular joint (TMJ) resulted in normal skeletal relation, the result of the subcondylar fractures seemed to be a deviation of the sy towards the nonfractured side. In cases of condylar head and neck fractures a deviation towards the fractured side frequently occurred. In four of the five children in whom normal skeletal relation in the TMJ was not obtained, the sy deviated towards the condylar fracture side. In the majority of the adulsts, a deviation towards the condylar fracture side occurred irrespective of the level of the condylar fracture.

Adult↗
PubMed1977

Condylar fractures of the mandible. I. Classification and relation to age, occlusion, and concomitant injuries of teeth and teeth-supporting structures, and fractures of the mandibular body.

In 123 individuals, 138 fractures of the mandibular condyle were classified with respect to fracture level, dislocation at the fracture level, and condylar head relation to the articular fossa. The age of the patient and the location of the most distal occlusal contact were recorded as well as teeth injuries and concomitant fractures of the mandibular body. The position of the most distal occlusal contact did not influence the dislocation of the condylar fragment. Teeth injuries such as fractures and luxation were found to be associated with condylar head or neck fractures, whereas the concomitant fractures of the mandibular body were mostly seen with the subcondylar fractures. Teeth injuries as well as concomitant fractures of the mandibular body were found more frequently in patients with bilateral than unilateral condylar fractures. Fractures of teeth in the molar and bicuspid regions were most frequent on the condylar fracture side, while the concomitant fractures of the mandibular body were located to the contralateral side. Medial angulation of the condylar fragment with lateral override at the fracture level was the typical fracture in adults, and angulation without override the characteristic fracture in growing individuals. Medical override occurred both in children and in adults and seemed to be the result of more severe trauma to the chin.

Accidents↗
PubMed1977

Characterization of hybrid plasmids carrying individual ribosomal ribonucleic acid transcription units of Escherichia coli.

We have screened the strains with ColE1 hybrid plasmids constructed by Clarke and Carbon (Cell 9:91-99, 1976) for the presence of ribosomal ribonucleic acid (rRNA) genes on the plasmids and identified 16 strains whose plasmids carry rRNA genes. The structures of these 16 plasmids were compared by heteroduplex analysis, and the plasmids were classified into six groups on the basis of their chromosomal origins. Homology with known transducing-phage deoxyribonucleic acids and genetic mapping have assigned locations on the Escherichia coli chromosome to three of the six groups. These are rrnB near rif at 88 min, rrnC near ilvE at 83 min, and rrnD near aroE at 71 min. A fourth group is probably rrnA at 85 min (T. Ikemura and M. Nomura, Cell, 11:779-793, 1977). We conclude that the minimum number of rRNA transcription units per haploid chromosomes is seven, that is, the six groups identified in this work plus a known operon (rrnE near metA at 89 min) that we failed to find among the hybrid plasmids. This heteroduplex analysis also suggests that there are only two kinds of rRNA operons with respect to their spacer region; three of the six rRNA operon groups studied here have one kind, whereas the remaining three have the other kind.

Bacterial Proteins↗
PubMed1976

Transfer RNA genes between 16S and 23S rRNA genes in rRNA transcription units of E. coli.

We have identified genes for tRNAGLU/2 on the transducing phages o80d3ilvsu7+ (see Ohtsubo et al., 1974) and lambdarifd18 (Kirschbaum and Konrad, 1973), and a gene for tRNAlle/1 on the transducing phage o80rifr (Konrad, Kirschbaum, and Austin, 1973). All these phages have previously been shown to carry genes for rRNA (Ohtsubo et al., 1974; Lindahl et al., 1975; Jaskunas et al., 1975a). We have analyzed the position of these tRNA genes by hybridizing purified RNAs to restriction fragments of the phage DNA. The tRNA genes are located inside the rRNA transcription unit in the spacer region between the 16S and 23S rRNA genes.

Chromosome Mapping↗
PubMed1976

Synthesis of ribosomal RNA in E. coli: analysis using deletion mutants of a lambda transducing phage carrying ribosomal RNA genes.

Transducing phage lambdarifd18 carries on rRNA transcription unit containing genes for 5S, 16S, and 23S rNAs and also tRNAGlu/2. Mutants were isolated from this phage that carry deletions removing various amounts of the distal end of this transcription unit. These deletions were physically mapped on the lambdarifd18 phage genome. Synthesis of rRNAs and of tRNAGlu/2 was examined in ultraviolet-irradiated E. coli cells infected with lambdarifd18 or with various deletion mutants. It was observed that mutant phages in which the distal end (the 5S rRNA gene and a part of the 23S rRNA gene) of the rRNA transcription unit is deleted can still synthesize both 16S rRNA (or its precursor) and tRNAGlu/2. Apparently, the post-transcriptional cleavage that produces these RNA molecules does not require the presence of the entire transcription unit, that is, it can take place without the complete structure of the transcript ("30S pre-ribosomal RNA"). In addition, the experimental results support the gene order, 16S rRNAGlu/2, 23S rRNA, and 5S rRNA genes, in the rRNA transcription unit carried by lambdarifd18.

Chromosome Mapping↗
PubMed1976

DNA-dependent in vitro synthesis of fibosomal proteins, protein elongation factors, and RNA polymerase subunit alpha: inhibition by ppGpp.

We have previously shown that the synthesis of ribosomal proteins (r proteins) in E. coli cells is under stringent control (Dennis and Nomura, 1974). Since guanosine tetraphosphate (ppGpp) has been implicated in stringent control, we examined the effects of ppGpp on the in vitro synthesis of r proteins directed by DNA from transducing phage lambdafus3 and lambdarifd18. lambdafus3 carries genes for protein elongation factors EF-Tu and EF-G, and RNA polymerase subunit alpha, in addition to genes for approximately 27 r proteins. lambdarifd18 carries genes for EF-Tu, RNA polymerase subunits beta and beta1, and a set of rRNAs, in addition to genes for approximately five r proteins. We have shown that low concentrations of ppGpp (0.2-0.3 mM) specifically inhibit DNA-dependent r protein synthesis in this system, and that this inhibition takes place directly, rather than as a consequence of the inhibition of rRNA synthesis by ppGpp. In addition, we have also shown that ppGpp inhibits the synthesis of EF-G, EF-Tu, and RNA polymerase subunit alpha, as well as rRNAs.

Colicins↗