PubMed Health⌕ Search

Biomedical subjects

F Severin

Publications and source records attributed to F Severin.

15 recordsLinked to original sources
PubMed2003

Urine mutagenicity and lymphocyte DNA damage in fruit growers occupationally exposed to the fungicide captan.

AIMS: To determine haematological parameters, urine mutagenicity (on three Salmonella typhimurium strains), and DNA damage (using the comet assay) in mononuclear leucocytes of farmers before and after a one-day spraying period of pear and apple trees with the fungicide captan in usual conditions. METHODS: Fruit growers were exposed to captan during the 1998 (n = 12) and/or the 2000 spraying seasons (n = 17). Biological samples were collected on the morning of the day of spraying (S1), the evening after spraying (S2), and the morning of the day after (S3). The UK Predictive Operator Exposure Model (UK-POEM) was used to quantify pesticide exposure intensity. RESULTS: No effect was observed on haematological parameters for these two spraying seasons. Proportions of mutagenic urine samples did not significantly differ between S1 and S2/S3 sampling points. In contrast with strains TA97a and YG1041 mainly sensitive to frameshift mutations, a positive trend was observed between the difference (S3-S1) of mutagenic power on strain TA102 detecting base-pair mutations and the exposure predicted value given by UK-POEM, mainly due to parameters related to protective clothing. No significant variations in DNA damage levels were observed between S1 and S3, nor were correlations observed with parameters of pesticide exposure. CONCLUSIONS: A one-day spraying period with captan and other pesticides does not significantly induce DNA damages in mononuclear leucocytes. In contrast, an inefficient protective clothing could correlate with an increase in urine mutagenicity as assessed by the TA102 tester strain.

Adult↗
PubMed2001

Correct spindle elongation at the metaphase/anaphase transition is an APC-dependent event in budding yeast.

At the metaphase to anaphase transition, chromosome segregation is initiated by the splitting of sister chromatids. Subsequently, spindles elongate, separating the sister chromosomes into two sets. Here, we investigate the cell cycle requirements for spindle elongation in budding yeast using mutants affecting sister chromatid cohesion or DNA replication. We show that separation of sister chromatids is not sufficient for proper spindle integrity during elongation. Rather, successful spindle elongation and stability require both sister chromatid separation and anaphase-promoting complex activation. Spindle integrity during elongation is dependent on proteolysis of the securin Pds1 but not on the activity of the separase Esp1. Our data suggest that stabilization of the elongating spindle at the metaphase to anaphase transition involves Pds1-dependent targets other than Esp1.

Anaphase↗
PubMed2001

Stu2 promotes mitotic spindle elongation in anaphase.

During anaphase, mitotic spindles elongate up to five times their metaphase length. This process, known as anaphase B, is essential for correct segregation of chromosomes. Here, we examine the control of spindle length during anaphase in the budding yeast Saccharomyces cerevisiae. We show that microtubule stabilization during anaphase requires the microtubule-associated protein Stu2. We further show that the activity of Stu2 is opposed by the activity of the kinesin-related protein Kip3. Reexamination of the kinesin homology tree suggests that KIP3 is the S. cerevisiae orthologue of the microtubule-destabilizing subfamily of kinesins (Kin I). We conclude that a balance of activity between evolutionally conserved microtubule-stabilizing and microtubule-destabilizing factors is essential for correct spindle elongation during anaphase B.

Anaphase↗
PubMed2000

Tumor necrosis factor induces hyperphosphorylation of kinesin light chain and inhibits kinesin-mediated transport of mitochondria.

The molecular motor kinesin is an ATPase that mediates plus end-directed transport of organelles along microtubules. Although the biochemical properties of kinesin are extensively studied, conclusive data on regulation of kinesin-mediated transport are largely lacking. Previously, we showed that the proinflammatory cytokine tumor necrosis factor induces perinuclear clustering of mitochondria. Here, we show that tumor necrosis factor impairs kinesin motor activity and hyperphosphorylates kinesin light chain through activation of two putative kinesin light chain kinases. Inactivation of kinesin, hyperphosphorylation of kinesin light chain, and perinuclear clustering of mitochondria exhibit the same p38 mitogen-activated kinase dependence, indicating their functional relationship. These data provide evidence for direct regulation of kinesin-mediated organelle transport by extracellular stimuli via cytokine receptor signaling pathways.

Animals↗
PubMed1999

Rab5 regulates motility of early endosomes on microtubules.

The small GTPase Rab5 regulates membrane docking and fusion in the early endocytic pathway. Here we reveal a new role for Rab5 in the regulation of endosome interactions with the microtubule network. Using Rab5 fused to green fluorescent protein we show that Rab5-positive endosomes move on microtubules in vivo. In vitro, Rab5 stimulates both association of early endosomes with microtubules and early-endosome motility towards the minus ends of microtubules. Moreover, similarly to endosome membrane docking and fusion, Rab5-dependent endosome movement depends on the phosphatidylinositol-3-OH kinase hVPS34. Thus, Rab5 functionally links regulation of membrane transport, motility and intracellular distribution of early endosomes.

Biological Transport↗
PubMed1998

Structural changes at microtubule ends accompanying GTP hydrolysis: information from a slowly hydrolyzable analogue of GTP, guanylyl (alpha,beta)methylenediphosphonate.

Microtubules are dynamic polymers that interconvert between periods of slow growth and fast shrinkage. The energy driving this nonequilibrium behavior comes from the hydrolysis of GTP, which is required to destabilize the microtubule lattice. To understand the mechanism of this destabilization, cryo-electron microscopy was used to compare the structure of the ends of shrinking microtubules assembled in the presence of either GTP or the slowly hydrolyzable analogue guanylyl (alpha,beta)methylenediphosphonate (GMPCPP). Depolymerization was induced by cold or addition of calcium. With either nucleotide, we have observed curled oligomers at the ends of shrinking microtubules. However, GDP oligomers were consistently more curved than GMPCPP oligomers. This difference in curvature between depolymerizing GDP and GMPCPP protofilaments suggests that GTP hydrolysis is accompanied by an increase in curvature of the protofilaments, thereby destabilizing the lateral interactions between tubulin subunits in the microtubule lattice.

Animals↗
PubMed1994

Detection of adeno-associated virus DNA in human genital tissue and in material from spontaneous abortion.

The human helper virus-dependent parvovirus, adeno-associated virus (AAV) has never been associated with disease in humans [Berns et al. (1987): Advances in Virus Research 32:243-306; Siegl et al. (1985): Intervirology 23:61-73]. However, in pregnant mice, infection with AAV induces early abortion [Botquin et al. (1993): Journal of Cancer Research and Clinical Oncology 119:24]. We investigated whether this common human virus may be found in human genital tissue or in curettage material from spontaneous abortion. Using the polymerase chain reaction (PCR) AAV type 2 DNA was amplified in histological sections of 19 of 30 biopsies of the uterine mucosa. In addition, AAV-2 DNA was detected in abortion material during the first trimester of pregnancy (12/30 cases were positive) but not in material of abortion from the second or third trimester (9 cases). Whereas in tissues from the uterus AAV DNA was found only by PCR, large amounts of viral DNA were detectable by Southern blot analysis in abortion material. In situ hybridization revealed DNA of AAV to be present in the villous moiety (trophoblast) of the placenta but not in the embryo or decidua. in the same cells, AAV proteins (including the replication-associated rep proteins) were detected by immunofluorescence analysis. These results suggest (1) that AAV infects the uterine mucosa (possibly persistently) and (2) that it can replicate in trophoblast cells. This might disturb placenta development and may play a role in early miscarriage.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Spontaneous↗
PubMed1990

Ludwig's angina and mediastinitis due to Streptococcus milleri: usefulness of computed tomography.

Despite intensive use of antibiotics, Ludwig's angina remains a potentially lethal infection because of the risk of upper airway obstruction and spread into the mediastinum. We present two patients who survived mediastinitis complicating Ludwig's angina due to Streptococcus milleri. Computed tomography performed early in the course of the disease detected pus collections and directed appropriate drainage procedures.

Abscess↗
PubMed1985

Subjective sensitization to tonic heat as an indicator of thermal pain.

In 144 healthy subjects tonic heat stimuli were applied with a contact thermode and systematically varied with respect to 3 parameters: temperature T, rate of temperature change RTC, and duration D. In addition, the stimulus temperature at which the first sensation of pain occurred was produced by some subjects. In both types of experiments, subjects compared heat intensity felt at the beginning and the end of the stimulus and then set stimulus temperature to correspond with their initial sensation. The direction of this temperature change (delta T) indicates whether the subject senses an augmentation or a diminution of heat intensity. There was a parallel occurrence of pain and sensitization to sustained heat. The average skin temperature of the point of transition from adaptation to sensitization was equal to the average pain threshold temperature. The temperature change response maintained individual differences of thermal and pain sensitivity and was highly consistent for each subject. Potential applications of the procedure in clinical and experimental pain research are discussed.

Adaptation, Physiological↗
PubMed1984

[Proof of TNS effect using experimental heat pain].

By means of experimentally induced heat pain, the effectiveness of transcutaneous electrical nerve stimulation (TNS) was studied in 51 healthy volunteers. TNS produces an elevation of the lower range of sensitiveness to pain ("elevated pain threshold") and hence pain relief. The findings are compared with neurophysiological results from leads of polymodal human C-fibres and spinothalamic tract (dorsal horn) neurons. Their importance for clinical pain syndromes is discussed.

Adult↗