Search PubMed⌕ Search

Biomedical subjects

K Kaiser

Publications and source records attributed to K Kaiser.

At least 91 records · Page 5Linked to original sources
PubMed1991

Glutathione depletion during experimental damage to rat skeletal muscle and its relevance to Duchenne muscular dystrophy.

1. The release of glutathione has been studied in comparison with the release of creatine kinase from isolated rat soleus muscles subjected to certain forms of experimental damage. 2. Excessive electrically stimulated contractile activity or treatment of muscles with the mitochondrial inhibitor, 2,4-dinitrophenol, induced a substantial release of both creatine kinase and glutathione and a reduction in the total glutathione content of the muscle. The time course of this release and depletion indicates that the efflux of the two molecules is not directly related and that a reduction in muscle glutathione content does not occur before cytosolic enzyme release. 3. 2,4-Dinitrophenol-stimulated release of creatine kinase was significantly reduced by the omission of external calcium from the incubation media, but glutathione release and depletion was relatively unaffected by this. Deliberate elevation of the muscle intracellular calcium content with the calcium ionophore, A23187, induced a substantial loss of creatine kinase, but had no significant effect on the release of glutathione. 4. Muscle biopsies from patients with Duchenne muscular dystrophy were found to have an elevated content of glutathione and an equivalent protein-thiol content compared with control subjects. 5. We conclude that, although release of glutathione from skeletal muscle occurs after excessive contractile activity or inhibition of mitochondrial metabolism, this is not a key step in the damaging processes leading to cytosolic enzyme release, neither is it relevant to the ongoing damage to skeletal muscle which occurs in patients with Duchenne muscular dystrophy.

2,4-Dinitrophenol↗
PubMed1991

Creatine kinase and prostaglandin E2 release from isolated Duchenne muscle.

We studied the release of creatine kinase (CK) activity and prostaglandin E2 (PGE2) from isolated strips of biceps muscle from patients with Duchenne muscular dystrophy and nondystrophic control patients. CK release was significantly higher from the dystrophic samples than controls during the initial period of incubation, but this difference reduced with time of incubation. Immediate immersal of muscle strips into calcium-free bathing medium reduced the initial difference between the efflux from dystrophic and nondystrophic samples, whereas treatment with the calcium ionophore maintained the difference between the groups throughout the period of incubation (150 minutes). These results support the hypothesis that the lack of dystrophin in Duchenne muscle leads to damage to the tissue via a failure of calcium homeostasis. PGE2 release from the muscle strips followed a similar pattern to CK activity, supporting the possibility that, at least partly, the calcium-mediated damage involves activation of phospholipid hydrolysis.

Adolescent↗
PubMed1990

From gene to phenotype in Drosophila and other organisms.

The growing number of cloned eukaryotic genes lacking a defined or proven biological function poses a major challenge in 'reverse genetics'. A method is described here that permits efficient screening for new lesions in, or close to, genes corresponding to cloned DNA sequences of interest. The technique involves transposon mutagenesis, followed by screening of DNA isolated from a population of mutagenised individuals (or their progeny) for evidence that the population contains at least one individual in which transposon insertion has occurred at the target locus. Detection of rare individuals within the population is facilitated by the use of the polymerase chain reaction (PCR). Once recognised, specific individuals (or their progeny) are isolated from the population by a process of sib-selection. In cases where insertion of the transposon has occurred close to, but not within, the target locus, secondary events involving imprecise excision of the transposon will nonetheless allow the isolation of mutant individuals. Though the method was developed specifically for the transposon-mutagenesis of Drosophila, extensions to other organisms and to other mutagenic strategies are feasible and some of the possibilities are discussed.

Animals↗
PubMed1990

"Site-selected" transposon mutagenesis of Drosophila.

Despite the wide range of techniques that can be brought to bear on the study of basic processes in Drosophila, there are still deficiencies in our armory. One of these is an ability to select mutants in cases where the gene is known and has been cloned, but where we are ignorant of the associated phenotype. We describe here a solution to this problem as applied to a model system, the singed (sn) locus. Our method is a combination of classical genetics and molecular biology: sib selection plus the polymerase chain reaction. We have used the method to isolate rare individuals with P-element-induced alleles of sn merely by recognition of the DNA structures induced at the locus by transposon insertion. Phenotypic criteria were used only retrospectively to verify our diagnoses. There are obvious implications of this technique for the mutagenesis of other organisms.

Animals↗
PubMed1987

Oligodeoxyribonucleotides containing 1,3-propanediol as nucleoside substitute.

1,3-Propanediol was protected with one dimethoxytrityl residue and converted into the methoxy- and cyanoethoxyphosphoramidites 2a and 2b, respectively. Solid-phase oligonucleotide synthesis, employing the phosphoramidite 2a resulted in the dodecamers d(CGCGAATTCGCG) (6-9), in which dA or dT residues were replaced by 1,3-propanediol. These oligomers showed a high tendency to form hairpins. Their phosphodiester bonds between the 3'-position of a nucleoside and the propanediol moiety was not cleaved by snake venom phosphodiesterase.

Base Sequence↗
PubMed1986

Phosphoramidites of base-modified 2'-deoxyinosine isosteres and solid-phase synthesis of d(GCI*CGC) oligomers containing an ambiguous base.

Novel phosphoramidites (1,2) of appropriately protected 2'-deoxyinosine isosteres (I*) such as allopurinol 2'-deoxyribofuranoside (4a) and 7-deaza-2'-deoxyinosine (4b) have been synthesized. They were employed together with the phosphoramidite of 2'-deoxyinosine in solid-phase synthesis of d(GCI*CGC) hexamers (12a-d). From thermodynamic data of these alternating hexamers it was shown that allopurinol 2'-deoxyribofuranoside destabilizes such duplexes less strongly than 2'-deoxyinosine. Additionally, the phosphoramidite of 7-deaza-2'-deoxyinosine (2) exhibits an extraordinary stability of the N-glycosylic bond. Since the new phosphoramidites are structurally related to 2'-deoxyinosine, they can be used in the construction of hybridization probes containing an ambiguous base.

Amides↗
PubMed1986

Dosage compensation at the sgs4 locus of Drosophila melanogaster.

The X-linked sgs4 gene of Drosophila melanogaster encodes a salivary glue protein. Non-dosage-compensated alleles of this gene have been described by G. Korge, in which males accumulate only about half of the Sgs4 polypeptide as do females. We show that the Sgs4 mRNA levels in dosage-compensated and non-dosage-compensated strains parallel the levels of Sgs4 polypeptide. Korge's genetic analysis of one of the non-dosage compensated alleles suggests that dosage compensation is controlled by sequences that lie 5' to the coding region. Sequences important for regulating the absolute levels of transcription of sgs4 have been identified as residing within a region of 600 base-pairs 5' to the site of transcription initiation. We have sequenced this region from two non-dosage-compensated strains and find no significant deviation from the sequence of dosage-compensated alleles. We therefore conclude that sequences that act to mediate the dosage compensation of sgs4 must lie outside this 600 base-pair region.

Animals↗
PubMed1983

A third defective lambdoid prophage of Escherichia coli K12 defined by the lambda derivative, lambdaqin111.

We describe the isolation and characterization of a new Q-independent substitution mutant of lambda, lambdaqin111, which differs from other characterized Q-independent lambda phages. This mutant defines a new lambda-like prophage in the bacterial chromosome, as seen by homologous recombination between lambdaqin111 and the host DNA and by DNA/DNA hybridization methods. Genetic and electron microscopy data show that this new prophage carries, at least, genes analogous to Q-S-R of lambda and also a cos site functionally identical to lambda cos. It is located near 34 min on the Escherichia coli K12 map, i.e. in the same region but at a different site from the defective Rac prophage.

Bacteriophage lambda↗
PubMed1981

Rac-E. coli K12 strains carry a preferential attachment site for lambda rev.

Lambda rev is a hybrid lambdoid phage formed by recombination between lambda and a defective lambdoid prophage (Rac) present in most E. coli K12 derivatives. We show here that three independently derived Rac-E. coli K12 strains are specifically deleted for the entire Rac prophage consistent with loss of Rac by excisive recombination between hybrid attachment sites that flank the prophage (c.f. excision of a lambda prophage). lambda rev, in which int and PP' of lambda have been replaced by integrative recombination genes and an attachment site derived from Rac (Gottesman et al. 1974), integrates site-specifically and in the correct orientation at the preferential attachment site generated by Rac excision.

Attachment Sites, Microbiological↗
PubMed1980

The origin of Q-independent derivatives of phage lambda.

lambda qsr' (Q-independent) phages are characterised by the replacement of the region of the lambda genome that contains Q, S, R, and the late gene promoter, P'R, with host-derived DNA that codes for functions analogous to those deleted. Restriction endonuclease analysis and DNA/DNA hybridisation methods have been used to show that lambda p4 and lambda qin A3, two such Q-independent phages, are the product of recombination between lambda and a defective lambdoid prophage (the qsr' prophage) located at an as yet unidentified site in the E. coli K 12 chromosome. The qsr' prophage is distinct from the defective lambdoid prophage Rac (Kaiser and Murray 1979). In the E. coli K12 strain AB1157 from which lambda qsr' phages cannot be generated, the qsr' prophage has suffered an internal deletion. That the qsr' prophage appears not to carry a full complement of essential late genes suggests one explanation for its apparently defective nature.

Bacteriophage lambda↗
PubMed1980

On the nature of sbcA mutations in E. coli K 12.

We have recently shown (Kaiser and Murray 1979) that many E. coli K 12 strains carry a defective prophage (Rac) located a few minutes clockwise of the trp operon on the genetic map. The Rac genome contains recE, the determinant for the ATP-independent exonuclease, ExoVIII. E. coli K 12 strains which carry sbcA mutations express recE constitutively. This paper describes an investigation of several such strains. We show that the SbcA phenotype may arise from more than one type of mutational change. The most readily explained SbcA phenotype is that of sbcA8 strains in which a large section of the Rac genome (including one hybrid attachment site and probably the prophage repressor gene) is deleted. Three sbcA- strains carry multiple (and probably tandemly repeated) copies of the Rac genome while two others carry a single Rac prophage that is indistinguishable in its hybridisation behaviour from that carried by sbcA+ strains.

Bacteriophage lambda↗
PubMed1979

Physical characterisation of the "Rac prophage" in E. coli K12.

We confirm the hypothesis of Low (1973) that many E. coli K12 strains contain a prophage (the Rac prophage) located a few minutes clockwise of the trp operon on the genetic map. We have used restriction endonucleases and 32P-labelled probes to construct a physical map of this prophage. Some E. coli K12 strains, including AB1157, have lost the entire prophage, apparently by a specific deletion. This is consistent with prophage excision by site-specific recombination. lambda reverse (lambda rev) phages (Zissler et al., 1971) are recombination proficient derivatives of phage lambda in which the phage recombination functions have been replaced by analogous functions (RecE) derived from the host chromosome (Gottesman et al., 1974; Gillen et al., 1977). Our data support the origin of lambda rev plages by recombination between lambda and the Rac prophage following excision of the Rac prophage from the E. coli chromosome. Important experimental data are included in the Figure legends.

Chromosome Mapping↗
PubMed1978

[A case of congenital double pyloric canal (author's transl)].

In the case of 47-year-old patient who had been suffering for several months from a duodenal ulcer disease, a so called double pylorus was traced by applying fiberoptic gastroscopy. At the same time proof was found for the ulcera duodeni. Owing to the fiberoptic result of two regularly pyloric canals it was already doubted, that this was only a question of a secondary pyloro duodenal fistula caused by peptic ulcer. A particular and differentiating pathological anatomical examination of the surgical specimen showed as a result, that the patient was suffering from a congenital duplication of the pyloric canal by a pyloric ligament. The duodenal ulcers, proofed by x-ray examination and gastroscopy, were recognised as a secondary disease of a locus minoris resistentiae.

Congenital Abnormalities↗