Biomedical subjects

Raluca Dumitru

Publications and source records attributed to Raluca Dumitru.

6 recordsLinked to original sources

PubMed2017

Rapid DNA replication origin licensing protects stem cell pluripotency.

Complete and robust human genome duplication requires loading minichromosome maintenance (MCM) helicase complexes at many DNA replication origins, an essential process termed origin licensing. Licensing is restricted to G1 phase of the cell cycle, but G1 length varies widely among cell types. Using quantitative single-cell analyses, we found that pluripotent stem cells with naturally short G1 phases load MCM much faster than their isogenic differentiated counterparts with long G1 phases. During the earliest stages of differentiation toward all lineages, MCM loading slows concurrently with G1 lengthening, revealing developmental control of MCM loading. In contrast, ectopic Cyclin E overproduction uncouples short G1 from fast MCM loading. Rapid licensing in stem cells is caused by accumulation of the MCM loading protein, Cdt1. Prematurely slowing MCM loading in pluripotent cells not only lengthens G1 but also accelerates differentiation. Thus, rapid origin licensing is an intrinsic characteristic of stem cells that contributes to pluripotency maintenance.

Cell Cycle↗

PubMed2006

Farnesol-induced apoptosis in Aspergillus nidulans reveals a possible mechanism for antagonistic interactions between fungi.

The dimorphic fungus Candida albicans secretes farnesol, which acts as a quorum-sensing molecule and prevents the yeast to mycelium conversion. In this study we examined the effect of farnesol in the filamentous fungus Aspergillus nidulans. We show that externally added farnesol has no effect on hyphal morphogenesis; instead, it triggers morphological features characteristic of apoptosis. Additional experiments suggest that mitochondria and reactive oxygen species (ROS) participate in farnesol-induced apoptosis. Moreover, the effects of farnesol appear to be mediated by the FadA heterotrimeric G protein complex. Because A. nidulans does not secrete detectable amounts of farnesol, we propose that it responds to farnesol produced by other fungi. In agreement with this notion, growth and development were impaired in a farnesol-dependent manner when A. nidulans was co-cultivated with C. albicans. Taken together, our data suggest that farnesol, in addition to its quorum-sensing function that regulates morphogenesis, is also employed by C. albicans to reduce competition from other microbes.

Antibiosis↗

PubMed2005

Biologically active fluorescent farnesol analogs.

We describe ten polyene analogs of farnesol, typified by 3,7,11-trimethyl-2,4,6,8,10-dodecapentenaldehyde oxime, which preserve the length, cross-section, and approximate hydrophobicity of farnesol. Four of the ten display strong quorum-sensing activity in the human pathogen Candida albicans, with IC(50) values for inhibition of germ-tube formation as low as 10 microM. The polyenes display absorption maxima between 320 and 380 nm, with the extinction coefficients for the oximes approaching 100,000. All but two of the analogs are fluorescent, with excitation maxima varying over the range of 320-370 nm. Oxime anti-4, which can undergo fluorescence excitation at wavelengths beyond 400 nm, is demonstrated to be useful for confocal fluorescence microscopic imaging of fungal cells. The farnesol analogs are also expected to be useful for detection of farnesol binding proteins and in determination of farnesol pharmacokinetics.

Candida albicans↗

PubMed2005

Farnesol concentrations required to block germ tube formation in Candida albicans in the presence and absence of serum.

Concentrations of (E,E)-farnesol needed to inhibit germ tube formation were determined for Candida albicans strains A72 and SC5314 by using six different conditions known to trigger germination. For defined media, 1 to 2 microM farnesol was sufficient. However, with serum at 2 to 20%, up to 250 microM farnesol was required. Farnesol blocked germ tube formation but did not block elongation of existing germ tubes.

Candida albicans↗

PubMed2004

High phosphate (up to 600 mM) induces pseudohyphal development in five wild type Candida albicans.

A method is described for the formation of nearly 100% pseudohyphae populations of wild-type Candida albicans A72. The method employs fungal growth at 37 degrees C (ca. 5x10(6) cells/ml) in a glucose-proline-N-acetyl-glucosamine medium supplemented with up to 600 mM phosphate (KH(2)PO(4)/K(2)HPO(4) 1:1) at pH 6.5. Four other strains of C. albicans (MEN, 10261, SG5314 and CAI-4) also formed pseudohyphae under these conditions, although the phosphate response profiles differed in the concentration required for each strain to form pseudohyphae.

Candida albicans↗

PubMed2004

Defined anaerobic growth medium for studying Candida albicans basic biology and resistance to eight antifungal drugs.

The polymorphic fungus Candida albicans is one of the most versatile opportunistic pathogens in humans. Many organs of the human body are potential targets for infection by this pathogen, but infection is commonly localized in the gastrointestinal tract, an environment providing anaerobic growth conditions. We describe a chemically defined anaerobic growth medium for four strains of Candida albicans (A72, SC5314, MEN, and 10261). It is a defined liquid glucose-phosphate-proline growth medium supplemented with oleic acid, nicotinic acid, and ammonium chloride. The cells did not require or respond to added ergosterol. Oleic acid and nicotinic acid are growth factors which are required only for the anaerobic growth of C. albicans. An important technical feature of this study was the use of anaerobically grown inocula to study anaerobic growth. Anaerobically, the cells grew exclusively as mycelia at 25, 30, and 37 degrees C. The doubling time at 30 degrees C was ca. 20 h. The cells did not produce farnesol and did not respond to exogenous farnesol, and they were resistant to the highest tested levels of amphotericin B and four of the azole antifungals. We suggest that the anaerobic growth of C. albicans may contribute to the trailing end point phenomenon and the resistance of C. albicans biofilms to antifungal drugs.

Anaerobiosis↗