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B Kraft

Publications and source records attributed to B Kraft.

14 recordsLinked to original sources
PubMed1990

Developmental mechanisms regulating the rapid decrease in a cohesion glycoprotein mRNA in Dictyostelium function primarily at the level of mRNA degradation.

During the morphogenetic program in Dictyostelium discoideum, the transcript of the gene encoding the cohesion glycoprotein gp80 accumulates to a maximum level between 4 and 6 hr, (just prior to the onset of aggregation), remains high between 6 and 10 hr (the ripple to loose aggregate stages), and then decreases to less than 10% of the maximum level between 10 and 12 hr (the tight aggregate stage). The level of gp80 transcript also decreases precipitously at the time of the erasure event in the program of dedifferentiation, or when cAMP is added to a dedifferentiating cell population prior to the erasure event. In the dedifferentiation-defective mutant HI4, the cAMP-stimulated system for rapidly reducing the level of gp80 transcript is intact, but the mechanism functioning at the time of the erasure event is defective, demonstrating that the two reduction mechanisms are dissociable. By comparing the levels of gp80 transcript with the levels of in vitro transcription of the gene in isolated nuclei, it is demonstrated that the rapid reduction of gp80 transcript immediately after aggregation and immediately after addition of 10(-4) M cAMP are the result of increased transcript degradation. The rapid reduction of gp80 transcript at the erasure event may also be due to increased transcript degradation, but transcriptional regulation cannot be completely ruled out in this case.

Cell Adhesion Molecules↗
PubMed1989

Dictyostelium erasure mutant HI4 abnormally retains development-specific mRNAs during dedifferentiation.

The Dictyostelium mutant HI4 progresses through morphogenesis normally, but is defective in the reverse program of dedifferentiation. In contrast to dedifferentiating wild-type cells, HI4 cells retain the capacity to rapidly reaggregate well after the "erasure event" employing a nonchemotactic aggregation mechanism involving random collisions and cohesion. They also do not lose contact sites A (gp80) at the prescribed time in the dedifferentiation program. HI4 cells accumulate transcripts of the cysteine protease gene CP2 (formerly referred to as 16G1) and the cohesion glycoprotein gene gp80 at the correct times in the morphogenetic program, but abnormally retain these transcripts at high levels well after the prescribed times at which they are lost in wild-type cells during the reverse program of dedifferentiation. The retention of these mRNAs in HI4 cells after the erasure event is not due to abnormal maintenance of a high level of intracellular cAMP during dedifferentiation. The rapid reduction in the level of gp80 transcript which can be effected by the addition of cAMP prior to the erasure event in wild-type cells is also retained by HI4 cells well after the erasure event. The results suggest that cells possess at least two mechanisms for the reduction of gp80 transcript. One involves the immediate response to cAMP and may function during the forward program of development. The second functions specifically during the reverse program of dedifferentiation. It is this latter, erasure-specific mechanism which is selectively defective in the HI4 variant.

Blotting, Northern↗
PubMed1988

[Assessment of fluid content of the lung by thoracic radiography. Comparison of extravascular lung water measurement and results of radiological estimation methods].

Extravascular lung water (EVLW) was determined with the thermal-dye double-indicator method (119 individual measurements) in 23 patients in an intensive-care unit, and the results were compared with estimates made from largely standardized portable chest X-ray films, using the staging method of Sibbald as well as that of Halperin. There was a significant correlation with the measured EVLW for both methods. Radiologically "normal" films corresponded to a mean EVLW value of 8.4 ml/kg body-weight. Radiologically judged adjacent stages did not in all cases compare with corresponding measured EVLW values. But when EVLW values were clearly abnormal, the X-ray films always demonstrated massive interstitial or alveolar infiltrations. Measurement of EVLW enables one accurately to judge the fluid contents of the lung and is superior to the assessment of the chest X-ray film.

Adult↗
PubMed1988

A comparison of high frequency switching in the yeast Candida albicans and the slime mold Dictyostelium discoideum.

Recently, high frequency switching systems have been identified in the infectious yeast Candida albicans and the cellular slime mold Dictyostelium discoideum. In C. albicans, cells can switch at spontaneous frequencies as high as 10(-2) between seven general colony morphologies in the case of strain 3153A or between two major phenotypes in the white-opaque transition in strain WO-1. In the latter system, dramatic changes occur in cellular phenotype as well. In D. discoideum, cells can switch at spontaneous frequencies of roughly 10(-2) between a number of colony phenotypes which include alterations in developmental timing, blocks at particular morphogenetic stages, morphological aberrations, and aggregation-minus. In the C. albicans and D. discoideum switching systems, the following characteristics are shared: 1) a limited number of switch phenotypes; 2) heritability; 3) high frequency reversibility; 4) low and high frequency modes of switching; and 5) ultraviolet (UV) stimulation of switching of cells in a low frequency mode of switching.

Candida albicans↗
PubMed1988

High-frequency switching in Dictyostelium.

A high-frequency switching system is demonstrated to exist in Dictyostelium discoideum. Switch phenotypes are distinguished by colony morphology and include changes in developmental timing as well as blocks in morphogenesis. The switching system exhibits the following characteristics: (1) a "low" spontaneous frequency of switching (approximately 10(-2] in the parent strain; (2) stimulation of the basal level of switching roughly fivefold with low doses of ultraviolet light; (3) "high" spontaneous frequencies of switching (as high as 10(-1] in particular variant strains; (4) high spontaneous frequencies of interconvertibility between variant phenotypes; (5) high spontaneous frequencies of reversion to the wild-type phenotype; (6) a set of reproducible switch phenotypes; (7) heritability of switch phenotypes; and (8) a rough correlation between switch phenotype and switching frequency. The extraordinary similarity between the switching systems in D. discoideum and Candida albicans is discussed.

Dictyostelium↗
PubMed1987

Characterization of a timing mutant of Dictyostelium discoideum which exhibits "high frequency switching".

The preaggregative period of Dictyostelium discoideum is composed of two sequential rate-limiting components. The timing mutant FM-1 exhibits a decrease in the length of the preaggregative period and the interval between the maxifinger and early culminate II stage. In contrast, it is normal in all aspects of growth, in the sequence of morphogenetic stages, in spore formation, in the capacity to rapidly recapitulate morphogenesis, and in the erasure event and subsequent program of dedifferentiation. By the reciprocal shift experiment, it is demonstrated that FM-1 is completely missing the first of the two rate-limiting components comprising the preaggregative period. The FM-1 mutation is heritable and behaves as a single mutation mapping to linkage group II. However, the FM-1 variant switches at relatively high frequency to several other timing phenotypes with longer preaggregative periods which in turn switch at high frequency. The FM-1 phenotype is considered in terms of timing regulation, and the process of high frequency switching between timing phenotypes is compared to other newly discovered switching systems.

Animals↗
PubMed1978

[Radiological diagnosis and differential diagnosis of calcifications of the basal ganglia (author's transl)].

The radiological appearance and main features of calcifications of the basal ganglia in metabolic, toxic and hypoxemic disorders, degenerative and systemic diseases, tumors as well as infectious and parasitic lesions are described and demonstrated by typical radiographs. The roentgenological differential diagnosis and etiological classification are debated on occurence, incidence, localization, and topography with regard to individual structures of the basal ganglia, distribution pattern and according to the dimension, shape, margin and density pattern of these calcifications.

Basal Ganglia↗
PubMed1976

Comparative calcium ion determinations in plasma and whole blood with a new calcium ion analyzer.

A new Ca2+ analyzer has been used for the determination of Ca2+ in plasma and whole blood from normal subjects and patients with disorders of calcium metabolism. The results were nearly identical: the equation of the regression line was y=1.02x-0.037 and the coefficient of correlation r=0.998. The possibility of using whole blood for measurement with concomitant simplification of the anaerobic sample preparation is an obvious advantage.

Calcium↗