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Biomedical subjects

D Kaiser

Publications and source records attributed to D Kaiser.

At least 181 records · Page 10Linked to original sources
PubMed1984

Construction of Tn5 lac, a transposon that fuses lacZ expression to exogenous promoters, and its introduction into Myxococcus xanthus.

A promoterless trp-lac fusion fragment was inserted near one end of the bacterial transposon Tn5 in the correct orientation to fuse lacZ gene expression to promoters outside Tn5. The resulting transposon, Tn5 lac, retains the kanamycin-resistance gene of Tn5 and transposes in Escherichia coli at 6% the frequency of Tn5 to many different sites in a bacteriophage lambda target. Expression of beta-galactosidase, the product of the lacZ gene, from Tn5 lac insertions in phage lambda depends both on insertion into a transcription unit in the correct orientation and on the regulation of the promoter of the transcription unit, verifying that by transposition Tn5 lac can fuse lacZ expression to outside promoters. An insertion of Tn5 lac in bacteriophage P1 was isolated and used to introduce Tn5 lac into Myxococcus xanthus, a bacterium that undergoes multicellular development. Stable kanamycin-resistant transductants are obtained that contain no P1 DNA sequences but have Tn5 lac inserted at different sites in the Myxococcus chromosome. Individual transductants express different levels of beta-galactosidase. A chromogenic substrate of beta-galactosidase, 5-bromo-4-chloro-3-indolyl beta-D-galactoside, is toxic in Myxococcus when cleaved in large amounts. In principle, Tn5 lac could be used to assay transcription in any bacterium in which Tn5 can transpose and beta-galactosidase can be measured.

Bacteriophage lambda↗
PubMed1984

Concentrations of ceftriaxone in serum and lung tissue.

19 patients received an intravenous 5-min bolus injection of 2 g ceftriaxone at various times before thoracic surgery. Lung tissue concentrations of 31.8 micrograms/g could be maintained for at least 5 h. Serum and lung tissue concentrations of ceftriaxone are high enough to inhibit most organisms causing nosocomial and community-acquired respiratory tract infections.

Cefotaxime↗
PubMed1984

[Fever of unknown origin].

A 54-year-old man suffered from intermittent episodes of high fever up to 40 degrees C for a period of about 2 years. In 1945 he was wounded by a shell fragment entering the left lower thorax. Finally the combination of diagnostic procedures revealed the origin of the fever. A colonic fistula leading to the shell fragment in the spleen was found.

Colonic Diseases↗
PubMed1983

Insertions of Tn5 near genes that govern stimulatable cell motility in Myxococcus.

Insertions of transposon Tn5 were used to examine the genetics of motility mutants in Myxococcus. Fifteen independent insertions of Tn5 were isolated that were linked to seven different loci that govern motility. Among the motility mutants that can be stimulated to move transiently by contact with other cells, a one-to-one correspondence was confirmed between specificity of stimulation and genetic locus. There are six different specificities and six corresponding loci, as if each locus governs a different protein required for gliding motility.

Chromosome Mapping↗
PubMed1983

Avoidance of perinatal transmission of hepatitis B virus: is passive immunisation always necessary?

Screening of 8918 pregnant women revealed that 107 (1.2%) were HBsAg-positive. 92 of them (50 of German and 42 of predominantly Asian origin) have already delivered and were followed up for 12 months together with their infants. 14 infants of HBeAg-positive (or anti-HBe-negative) carrier mothers received a single dose of hepatitis B immunoglobulin (HBIG) immediately after birth, while 60 infants of anti-HBe-positive mothers were not immunised. 57 of the 60 "unprotected" children remained seronegative for HBsAg and HBeAg. 3 children showed HBs-antigenaemia immediately after birth; 2 of these lost HBsAg and developed anti-HBs after 6 and 9 months. The third lost HBsAg after 4 months without an antibody response developing. This suggests that the HBsAg particle only was transmitted rather than the whole virus. 12 of the 14 infants born to HBeAg-positive, or anti-HBe-negative carrier mothers were protected with one single high dose of HBIG. 2 had HBs-antigenaemia, 1 had HBeAg as well. These data show that in a West European population the risk of perinatally acquired HBV infection in the infants of anti-HBe-positive carrier mothers is small, and that passive immunisation of this group is not necessarily indicated.

Asia↗
PubMed1983

In situ transposon replacement and isolation of a spontaneous tandem genetic duplication.

Using a specialized transducing P1 phage carrying an insertion of Tn5-132, an insertion of Tn5-wt in the chromosome of Myxococcus xanthus, which codes for resistance to kanamycin, can be replaced with one of Tn5-132, which codes for resistance to tetracycline. That Tn5-132 in the daughter is inserted at the same location in the chromosome as Tn5-wt was in the parent was shown by a variety of physical and genetic tests. Southern blot hybridizations of restriction digests of daughter and parent DNAs probed for sequences homologous to Tn5 show that the physical location is the same. When KmR was transduced from the parent to the TcR daughter by the generalized transducing myxophage Mx4 or Mx8, all the transductants were TcS. Likewise, when the daughter was used as donor, TcR transductants of its KmR parent were KmS. Flanking markers that were linked to KmR in the parent were linked to TcR in the daughter. Spontaneous tandem genetic duplications of portions of bacterial chromosomes can be trapped by transducing a selectable marker from a donor to a recipient that has a different selectable marker at the same genetic location and selecting transductants with both markers. Using Tc-replacement, this technique can be applied to any region of the chromosome. We used it to isolate a spontaneous tandem duplication of part of the M. xanthus chromosome. The duplication was characterized by Southern blot hybridizations probed for Tn5-homologous DNA. It was also shown to be unstable by quantitation of loss of drug resistance. Transduction of the novel joint led to reconstruction of the duplication in the recipient strain. All these tests gave results consistent with the proposed structure. The methods described here are applicable to any bacterium into which transposons can be introduced, and for which some means of genetic exchange is available.

DNA Transposable Elements↗
PubMed1983

Pulmonary function testing in a general medical practice.

This study examined the feasibility and yield of spirometric screening in a general medicine clinic. Each of 354 randomly selected patients answered a questionnaire on respiratory symptoms and performed pulmonary function tests. Pulmonary testing required approximately two minutes and cost 95 cents per patient. Former smokers who stopped smoking because of symptoms displayed a higher prevalence of abnormalities than expected, and life-long smokers a lower prevalence (P less than 0.001). Fifty-three percent of current smokers had an abnormal pulmonary function test, and forty-two percent of these had no severe pulmonary symptoms. Pulmonary function tests performed in an outpatient clinic are rapid and expensive. Such tests demonstrate a large number of abnormalities which can be used to encourage smoking cessation.

Family Practice↗
PubMed1983

Developmental cell interactions in Myxococcus xanthus and the spoC locus.

The product(s) of the Myxococcus xanthus spoC locus is required for two multicellular activities in fruiting body development, rippling and sporulation. Ripples, which are formed early in development, are spatially separated ridges of cells that move synchronously. Myxospores are heat-resistant resting cells that are formed near the end of the developmental process. To investigate the function of spoC, it was cloned in an Escherichia coli plasmid, then transferred to M. xanthus by specialized transduction with coliphage P1. The plasmid, which cannot replicate in M. xanthus, integrated into the M. xanthus chromosome, producing two copies of the spoC locus in tandem. Cells containing one copy of a mutant allele and one copy of the wild-type allele displayed the wild-type phenotype. Cells containing two different mutant alleles failed to ripple or sporulate, implying that all four independent spoC mutations are in the same gene or unit of transcription. Homozygous mutant duplications arose from constructions in which DNA from a spo(+) donor was transduced into a spoC recipient, or vice versa, at an average frequency of 14%, indicating that gene conversion was a frequent event.

Journal Article↗
PubMed1983

Developmental cell interactions of Myxococcus xanthus: analysis of mutants.

A set of developmental mutants have been examined that behave as if defective in cellular interactions necessary for the formation of myxospores during fruiting body development. Sporulation is rescued in these mutants if they are mixed with wild-type cells. Complementation experiments with whole cells divide the mutants into four groups (A, B, C, and D). Mutants of group A appear to be less responsive to starvation, a condition that normally initiates development. Mutants of group D respond to starvation but fail to synthesize myxobacterial hemagglutinin, a protein normally synthesized midway in development. Mutants of groups B and C respond to starvation and synthesize hemagglutinin, but they can be distinguished genetically. Group C mutations all map in a single cluster near insertion omega 1519 of transposon Tn5, which is distant from group B mutations. Thus, each group represents a different defect in development. All of the mutants are induced to sporulate by glycerol. Therefore, we argue that sporulation during fruiting body development depends on several prior interactions between cells.

Mutation↗