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Biomedical subjects

D Kaiser

Publications and source records attributed to D Kaiser.

At least 145 records · Page 8Linked to original sources
PubMed1989

asgB, a gene required early for developmental signalling, aggregation, and sporulation of Myxococcus xanthus.

The asgB genetic locus of Myxococcus xanthus specifies a function which is required early in the developmental pathway leading to aggregation and sporulation in fruiting bodies. The developmental defect of asgB mutants can be compensated by extracellular complementation using either intact wild-type cells or cell-free supernatants conditioned by developing wild-type cells. A Tn5 insertion was isolated closely linked to asgB480 and facilitated the cloning of both the wild-type (asgB+) and the mutant (asgB480) alleles in Escherichia coli plasmid. Tandem duplications of the asgB locus were constructed in M. xanthus; the completely wild-type phenotype of asgB+/asgB480 partial diploids implies that the asgB480 allele is recessive. This finding, along with extracellular complementation by wild-type cells, is consistent with the hypothesis that the asgB+ locus is required to produce a substance with an intercellular signalling function. At least part of the asgB gene was found to lie within a 1.2 kb SmaI DNA fragment. This 1.2 kb fragment, as well as smaller fragments derived from it, were used as DNA probes in RNA/DNA hybrid analyses of transcription in the asgB region. Two small mRNA species were detected, one about 650 bp long, and the other about 500 bp; the two species of mRNAs apparently overlap. Both mRNAs are present in low, but approximately equal amounts, in vegetatively growing cells. This is consistent with the observation that asg mutants display a mutant vegetative phenotype (a change in colony color and spreading behavior) as well as defective development.

Blotting, Northern↗
PubMed1989

Percentages of maximal heart rate, heart rate reserve, and VO2peak for determining endurance training intensity in sedentary women.

The use of 60%-95% of maximal heart rate (HR max), heart rate reserve (HRR), and VO2peak as exercise training intensities was examined in sedentary women, and these intensities were related to HR and VO2 observed at the lactate threshold (LT) and fixed blood lactate concentrations of 2.0, 2.5, and 4.0 mM. Thirty-three subjects (means age = 32.5 +/- 3.9 yrs; means ht = 164.2 +2- 5.0 cm; means wt = 67.6 +/- 13.9 kg) completed a VO2/LT treadmill test using a level running protocol. The values at LT, 2.0, 2.5, 4.0 mM, and peak for VO2 were 22.3, 29.0, 31.0, 36.2, and 39.1 ml/kg.min-1, respectively; for velocity were 107.0, 128.9, 135.8, 152.8, and 164.4 m/min, respectively; and for HR were 142.1, 162.9, 169.4, 183.2, and 189.7 bts/min, respectively. The minimum intensity necessary for the majority of subjects to be above LT (n = 17) was 75% HR max while 90% HR max was required for the majority of subjects to be above 2.0 mM (n = 23) and 2.5 mM (n = 19). At 95% HR max 12 subjects were above 4.0 mM. For the majority of subjects to be above LT (n = 18), 55% HRR was necessary; 75%, 85%, and 95% HRR was required for the majority of subjects to be above 2.0 mM (n = 18), 2.5 mM (n = 19), and 4.0 mM (n = 20), respectively. For percent VO2peak, the intensities required for the majority of subjects to be above LT, 2.0 mM, 2.5 mM, and 4.0 mM were 55%, 75%, 80%, and 95% VO2peak, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Malignant chest wall infiltration in MR: comparison with CT and surgical findings].

CT and MRI were performed on 19 patients with pleura related thoracic tumors with respect to the detection of chest-wall invasion. All patients underwent surgery, which confirmed malignant infiltration in 16 cases, while this was excluded in three. CT showed chest-wall invasion in 12/19 patients. MRI demonstrated tumorous involvement in 16 patients. A reliable pattern of chest-wall invasion in MRI were high signal intensity lesions within the chest-wall in the T2-weighted images. However, increased signal intensity of pleural structures was found in inflammatory as well as in malignant lesions. MRI can prove the presence of chest-wall invasion when CT is equivocal.

Adult↗
PubMed1989

Physical mapping of the Myxococcus xanthus genome by random cloning in yeast artificial chromosomes.

Random segments of Myxococcus xanthus DNA were cloned in yeast artificial chromosomes (YACs) to construct a physical map of the genome. EcoRI restriction maps of 409 YAC clones with inserts averaging 111 kilobase pairs (kb) were determined. Comparison to the map of a 300-kb region of M. xanthus obtained from clones in Escherichia coli indicates that segments of DNA cloned in YACs are stably maintained in yeast and that their sequences accurately reflect the structure of the Myxococcus genome. The 409 YAC inserts were ordered within 60 map segments (contigs) by aligning their EcoRI restriction maps and by hybridization with 18 gene-specific DNA probes. These 60 map segments may represent the entire Myxococcus genome and could be used to organize its genetic information. This study illustrates the utility of YACs for cloning large segments of DNA and for reliable long-range genomic mapping.

Chromosome Mapping↗
PubMed1989

Gliding motility in Myxococcus xanthus: mgl locus, RNA, and predicted protein products.

Mutants of Myxococcus xanthus that had lost the ability to glide were examined to elucidate the mechanism of gliding motility. Nonmotile mutants resulting from a single mutational step were all defective at the same locus, mgl, which implied an important role for the mgl product(s) in gliding. Deletion experiments, transposon insertion mutagenesis, and genetic rescue of mgl mutants mapped the locus to a 1.6-kilobase segment of Myxococcus DNA. Two species of RNA that hybridized with mgl DNA were found both during vegetative growth and during the starvation-induced development of fruiting bodies, which also requires cell movement. The two RNA species, of 1.5 and 1.3 kilobases, had the same 5' to 3' orientation and overlapped extensively. The DNA sequences of mgl+ and of seven mgl mutants were determined. Each mutant differed from mgl+ by a single-base-pair change in the sequence. Two adjacent open reading frames were found in the sequence hybridizing to both species of mgl RNA. Six of the single-base-pair changes, each of which would result in a single-amino-acid change, and an insertion-produced mgl mutation were located in the downstream open reading frame. This open reading frame (of 195 amino acids) is therefore an mgl gene, called mglA. The function of the upstream open reading frame is not known with certainty, although it does contain one of the mgl mutant sites and could be a second mgl gene.

Amino Acid Sequence↗
PubMed1989

Genes required for developmental signalling in Myxococcus xanthus: three asg loci.

asg-carrying strains of Myxococcus xanthus arose in a selection for mutants defective in cell-cell signalling during fruiting body development. All 15 asg mutations examined were found to lie in one of three genetic loci, asgA, asgB, or asgC. The loci were defined by linkage to different insertions of transposon Tn5 and molecular cloning of asgA. asg mutants of all three types were deficient in the aggregation of cells into mounds of the sort that normally give rise to fruiting bodies. asg mutants were also deficient in spore formation; sporulation is normally one of the last steps in fruiting body development. Consistent with a requirement for cell-to-cell signalling, at 1 to 2 h asg+-carrying cells release a material called A-factor that can rescue development of asg mutants. asgA, asgB, and asgC mutants released 5% or less of the asg+ level of A-factor, as measured by bioassay. The experimental results are consistent with the hypothesis that a deficiency in A-factor production or release is the primary developmental defect in asg mutants and that aggregation and sporulation depend on A-factor. asg mutations at all three loci also changed the color and morphology of growing colonies, and failure to release A-factor may itself arise from a defect in growing cells.

Bacterial Adhesion↗
PubMed1989

dsg, a gene required for cell-cell interaction early in Myxococcus development.

dsg mutants of Myxococcus xanthus are conditionally defective in fruiting body development, including sporulation. Unable to develop on their own, these mutants can assemble fruiting bodies with spores if they are mixed with wild-type cells. To elucidate the developmental defect in dsg mutants by close comparison with wild type, such mutants have been backcrossed by transduction, using a closely linked insertion of transposon Tn5 for selection. Backcrossed dsg mutants form aggregates that are larger, less compact, and less symmetrical than dsg+ fruiting bodies. Also, the starvation-induced sporulation in dsg aggregates is delayed and reduced. However, dsg mutants can be induced by glycerol or dimethyl sulfoxide to sporulate at levels approaching those of wild type. dsg mutants may thus have a primary defect early in development which diminishes their capacity to aggregate and which indirectly decreases the number of fruiting body spores. The linked insertion of Tn5 also facilitated cloning the dsg gene. The cloned dsg+ allele was shown to be dominant to both the dsg-429 and dsg-439 alleles, and both mutant alleles were shown to belong to the same genetic complementation group. Subcloning of restriction fragments, deletions, and insertions of transposon Tn5 agree in locating the dsg gene to an 850-base-pair segment of the cloned region.

Cloning, Molecular↗
PubMed1989

dsg, a gene required for Myxococcus development, is necessary for cell viability.

Previous work identified the dsg gene as necessary for cell-cell interaction in Myxococcus xanthus. Point mutations of this gene, such as dsg-439, are viable, but insertions of Tn5 within the dsg gene (dsg::Tn5) are lethal. Partial diploids, dsg::Tn5/dsg+ or dsg::Tn5/dsg-429 or dsg::Tn5/dsg-439, are also viable, showing that the lethal effect of the haploid insertions is due to loss of function. Thus the evidence implies that the dsg gene is essential for viability as well as development, but its essential quality differs between growth and development because dsg-429 and dsg-439 mutants grow normally, but are unable to develop.

Chromosome Deletion↗
PubMed1989

[Fibrin gluing in spontaneous pneumothorax].

The article reports on the results of surgical thoracoscopy using the mediastinoscope in relapsing spontaneous pneumothorax and persisting spontaneous pneumothorax. This surgical method is performed under intubation anesthesia. Existing changes such as emphysematous bullae or fused strands are removed or cut. The parenchymatous defects occurring after surgical removal of bullae are bonded by means of 2 ml fibrin adhesive. 75% of the patients treated in this manner remain free from recurrences so that it was not necessary to perform thoracotomy although this had been originally indicated. Measures for pleurodesis that are not "on target" must be rejected, since they do not help in removing the morphological changes at the lung surface. Surgical thoracoscopy as described is, therefore, in some cases an alternative to classical thoracotomy.

Adult↗
PubMed1989

[Infrared coagulation in lung surgery].

Infrared coagulation (IRC) is a reliable method to stop surgical bleeding from the thoracic wall and proves to be superior to other forms of coagulation in this area. In pulmonary parenchyma IRC is used for sealing of parenchymal surfaces after atypical resections. Emphysematous bullae may be coagulated with IRC instead of over-swan. A main advantage in using IRC is that the surgical area not necessarily needs to be "dry" for application of IRC. Forced pressing of the IRC-applicator against the tissue prevents dissipation of light energy via running blood. There are no superficial carbonisations, instead there is coagulation inside the tissue.

Hemostasis, Surgical↗
PubMed1989

[Prognostic factors in diffuse malignant mesothelioma of the pleura].

Diffuse malignant pleural mesothelioma (DMM) is associated with a very poor prognosis and is only partially accessible to treatment. On the basis of a retrospective analysis, we made an attempt to identify possible factors that influence the prognosis. Between 1964 and 1986, 84 evaluable patients were treated: the ratio of male to female patients was 4.3:1, their average age being 58.5 +/- 11.9 (range: 21-82 years). The tumour types included 50% epithelial, 38% biphasic, and 12% mesenchymal tumours. The classification in accordance with the suggestions of Butchart revealed: I 10%, II 89%, III 0%, IV 1%. In 32% of the patients, treatment was purely symptomatic, in 42% a palliative surgical procedure with decortication of the tumour and tumour-pleurectomy was performed, while in 26% the palliative procedure was followed by adjuvant chemotherapy using doxorubicin and cisplatin. The median survival for the patients overall was 253 days. Parameters that were found not to correlate with the prognosis were: age, sex, exposure to asbestos, use of tobacco, pleural effusion, and growth behaviour in the thymus aplastic nude mouse. A significant influence was found for the histological type of the tumour and therapy administered, epithelial and biphasic tumour forms, as also surgical and combined surgical/chemotherapeutic treatment resulting in a more prolonged survival. On the basis of these results, surgical therapy should always be employed, despite the fact that there is almost always no curative option; postoperative adjuvant therapy is capable of further improving the prognosis.

Adult↗
PubMed1989

Prospective monitoring trial for carcinoma of colon and rectum after surgical resection.

In 1978, a prospective program was initiated to evaluate postoperative monitoring of patients after resection of carcinoma of the colon and rectum. The program included clinical examination, interval endoscopy, measurement of carcinoembryonic antigen (CEA), selected liver function tests (alkaline phosphatase and gamma glutamyl transferase) and roentgenologic testing: roentgenograms of the chest, barium enema, intravenous pyelogram (IVP) and computerized axial tomographic (CAT) scan. Of the initial 226 patients enrolled, 179 had at least one abnormal elevation of the CEA level, and in 70 (39 per cent), recurrence developed. Of the 70 with recurrence, 62 (89 per cent) had elevated CEA levels (greater than 3.0 nanograms per milliliter) prior to detection of recurrence by other means. Eight patients had normal levels (two were false-negative and the other six were tested at inappropriate times). Although other test results often complemented CEA, they were generally less sensitive for early detection. Selective use of these tests frequently documented site and extent of recurrence. The detection sensitivity of these other tests was highest with CAT scan (83 per cent), followed by barium enema and endoscopy (56 and 46 per cent). Forty-five patients underwent re-exploration. Recurrence was found in 42, of whom 23 had resectable disease (five of 11, liver; 17 of 24, local or pelvis, and one of one, lung). In three patients, nothing abnormal was found at exploration; two of these patients ultimately had metastases develop. The median survival time was 43 months and the estimated five year survival rate was 38 per cent. CEA is the best over-all indicator of early recurrence and frequent testing at short intervals is most important. Periodic clinical examination and selected other studies are also essential for early documentation of recurrence. Second-look surgical procedures appear beneficial for survival time in selected patients.

Carcinoembryonic Antigen↗
PubMed1989

[Indications for thoracoscopy in pleural empyema].

If the acute empyema of the pleura is not treated well in time via thoracic drainage and lavage, a cavitated empyema of the pleura may result. Such cavitated empyemas may be drained via surgical thoracoscopy using the mediastinoscope in intubation anaesthesia. Major surgery as represented by standard thoracoscopy is thus avoided. By intraoperative positive pressure breathing the fibrin deposits on the visceral pleural are torn, thus enabling maximum possible re-expansion of the lungs.

Adult↗
PubMed1988

A link between cell movement and gene expression argues that motility is required for cell-cell signaling during fruiting body development.

Nonmotile mutants of Myxococcus xanthus (Myxobacterales) failed to execute the morphogenetic movements required to shape a fruiting body. In addition, nonmotile mutants produced very few spores when plated for fruiting body development at cell densities appropriate for wild-type cells. At higher initial cell densities, the proportion of nonmotile cells that sporulate increased, indicating that one important function of motility in fruiting body development is to increase the local cell density. However, even at 10 times normal cell density, nonmotile cells sporulated at only 1% the wild-type level. This sporulation deficiency of nonmotile mutants accompanies an altered pattern of gene expression, monitored by using transcriptional fusions of lacZ to genes expressed at specific times during fruiting body development. Motility was not required for normal expression of five lac fusions that are expressed within the first 6 hr of fruiting-body development. However, the levels of expression from five lac fusions to later-expressed genes were reduced or abolished in nonmotile strains. beta-Galactosidase expression in these late Tn5 lac insertions was increased, and fruiting body development occurred in certain nonmotile strains that can be stimulated to move when mixed with a donor strain. This shows that motility itself is required because the stimulated cells are nonmotile genotypically. The nonmotile mutations had the same effect on developmental beta-galactosidase expression from these 10 lac fusions as an insertion mutation in the csg (formerly spoC) gene. csg mutants have a cell-cell interaction defect that blocks fruiting body development at approximately 6 hr. The similarity in the pattern of developmental expression of motility mutants and csg mutants suggests that motility is required for this csg-mediated cell-cell interaction.

Cell Movement↗