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D Janssens

Publications and source records attributed to D Janssens.

At least 19 recordsLinked to original sources
PubMed2005

Natural association of Gluconacetobacter diazotrophicus and diazotrophic Acetobacter peroxydans with wetland rice.

The family Acetobacteraceae currently includes three known nitrogen-fixing species, Gluconacetobacter diazotrophicus, G. johannae and G. azotocaptans. In the present study, acetic acid-producing nitrogen-fixing bacteria were isolated from four different wetland rice varieties cultivated in the state of Tamilnadu, India. Most of these isolates were identified as G. diazotrophicus on the basis of their phenotypic characteristics and PCR assays using specific primers for that species. Based on 16S rDNA partial sequence analysis and DNA: DNA reassociation experiments the remaining isolates were identified as Acetobacter peroxydans, another species of the Acetobacteraceae family, thus far never reported as diazotrophic. The presence of nifH genes in A. peroxydans was confirmed by PCR amplification with nifH specific primers. Scope for the findings: This is the first report of the occurrence and association of N2-fixing Gluconacetobacter diazotrophicus and Acetobacter peroxydans with wetland rice varieties. This is the first report of diazotrophic nature of A. peroxydans.

Acetobacter↗
PubMed2004

Reclassification of Lactobacillus kefirgranum Takizawa et al. 1994 as Lactobacillus kefiranofaciens subsp. kefirgranum subsp. nov. and emended description of L. kefiranofaciens Fujisawa et al. 1988.

Fourteen homofermentative lactic acid bacteria that were isolated from kefir grains and kefir fermented milks were assigned to either Lactobacillus kefiranofaciens or Lactobacillus kefirgranum, based on their characteristic morphotypes, phenotypic features and SDS-PAGE profiles of whole-cell proteins. Further genotypic analyses on representative strains from both taxa demonstrated that L. kefiranofaciens and L. kefirgranum share 100 % 16S rDNA sequence similarity and belong phylogenetically to the Lactobacillus acidophilus species group. DNA-DNA binding values of >79 % and analogous DNA G+C contents of 37-38 mol% showed that the strains studied belonged to one species: L. kefirgranum is a later synonym of L. kefiranofaciens. An emended description is proposed for L. kefiranofaciens. Due to the specific morphological and biochemical characteristics of these taxa in kefir grain formation, it is proposed that L. kefirgranum should be reclassified as L. kefiranofaciens subsp. kefirgranum subsp. nov.

Animals↗
PubMed2003

Aquaspirillum dispar Hylemon et al. 1973 and Microvirgula aerodenitrificans Patureau et al. 1998 are subjective synonyms.

The 16S rDNA sequences of [Aquaspirillum] dispar LMG 4329(T) and Microvirgula aerodenitrificans SGLY2(T) (=LMG 18919(T)) were found to be very similar (>99 %). DNA-DNA hybridizations between the two strains revealed a high level of DNA-DNA binding (84 %), showing that they represent a single species. M. aerodenitrificans and [A.] dispar were also phenotypically very similar. It is concluded that [A.] dispar and M. aerodenitrificans are subjective synonyms. As [A.] dispar was wrongly assigned to the genus Aquaspirillum, we propose that strains of [A.] dispar must be reclassified in the genus MICROVIRGULA: The name Microvirgula aerodenitrificans must be retained for the unified taxon since it is the type of the genus MICROVIRGULA:

DNA, Bacterial↗
PubMed2002

Re-examination of the genus Acetobacter, with descriptions of Acetobacter cerevisiae sp. nov. and Acetobacter malorum sp. nov.

Thirty-four Acetobacter strains, representing Acetobacter aceti, Acetobacter pasteurianus, Acetobacter pomorum, Acetobacter peroxydans, Acetobacter lovaniensis, Acetobacter estunensis, Acetobacter orleanensis, Acetobacter indonesiensis and Acetobacter tropicalis, were subjected to a polyphasic study that included DNA-DNA hybridizations, DNA base ratio determinations, 16S rDNA sequence analysis and phenotypic characterization. Two novel species are proposed, Acetobacter cerevisiae sp. nov. and Acetobacter malorum sp. nov. The type strains of these species are respectively LMG 1625T (= DSM 14362T = NCIB 8894T = ATCC 23765T) and LMG 1746T (= DSM 14337T).

Acetobacter↗
PubMed2002

Return to fertility in nulliparous and parous women after removal of the GyneFix intrauterine contraceptive system.

OBJECTIVE: To evaluate the return to fertility following removal of the GyneFix intrauterine implant system in women wishing to conceive. STUDY DESIGN: A retrospective study was performed on a sample of healthy, sexually active nulligravid/nulliparous and parous women. The participants were 18-41 years of age, with no apparent infertility problem, living in a stable relationship and planning to become pregnant. Women who changed their mind and did not wish to become pregnant immediately after intrauterine device (IUD) removal were excluded from the study. Women were evaluated in terms of rates of conception and fertility outcome. A total of 128 women were evaluated. RESULTS: The study shows that 119 out of 128 (93%) past users of GyneFix have conceived, accounting for a net cumulative pregnancy rate of 88% at 12 months and 99% after 2 years' observation. No statistical differences in pregnancy rates were found for age and duration of use of the IUD. A strong significant difference in pregnancy rate was shown (p = 0.007) between parous and nulligravid/nulliparous women. Seventy-seven women (66.9%) gave birth to a term infant. There were no stillbirths. Twenty-five women (21.8%) are pregnant at the time of writing. Five (4.4%) spontaneous abortions occurred and in eight women (6.9%) the pregnancy was terminated. There were no ectopic pregnancies. CONCLUSION: The results obtained compare favorably with those obtained in previous studies conducted following the removal of copper IUDs. The use of the frameless IUD does not affect future fertility in nulligravid/nulliparous and parous women wishing to become pregnant following removal of the device. Nulliparous women conceive significantly earlier than parous women.

Abortion, Induced↗
PubMed2001

Expression, refolding and crystallization of the OpcA invasin from Neisseria meningitidis.

OpcA is an integral outer membrane from the Gram-negative pathogen Neisseria meningitidis that plays a role in adhesion of meningococci to host cells. The protein was overexpressed in Escherichia coli in an insoluble form and a procedure developed for refolding by rapid dilution from denaturant into detergent solution. The refolded material was identical to native OpcA isolated from meningococci, as judged by overall molecular weight, migration on SDS-PAGE and reaction against monoclonal antibodies. Both native and recombinant OpcA crystallized under similar conditions to give an orthorhombic crystal form (P2(1)2(1)2), with unit-cell parameters a = 96.9, b = 46.3, c = 74.0 A. Complete data sets of reflections were collected from native and refolded OpcA to 2.0 A resolution.

Bacterial Proteins↗
PubMed2001

Differences between subcultures of the Mesorhizobium loti type strain from different culture collections.

Because of differences in the reported 16S rRNA gene sequence of the Mesorhizobium loti type strain available from different culture collections, we collected different subcultures of this strain and compared them by 16S rDNA sequencing, SDS-PAGE of whole-cell protein extracts and RAPD-PCR. Our results indicate that the 16S rDNA sequence differences can be explained by the presence of two different organisms in one of the subcultures. In addition, even for subcultures of the type strain that had identical 16S rDNA sequences, small differences could be observed in the protein profiles and in the RAPD-PCR patterns. These latter observations indicate that maintenance procedures necessary for long-term preservation by freeze-drying can cause subcultures of the same original strain to undergo changes, effectively leading to different fingerprints even though 16S rDNA sequences remain identical.

DNA Fingerprinting↗
PubMed2001

Classification of metal-resistant bacteria from industrial biotopes as Ralstonia campinensis sp. nov., Ralstonia metallidurans sp. nov. and Ralstonia basilensis Steinle et al. 1998 emend.

Thirty-one heavy-metal-resistant bacteria isolated from industrial biotopes were subjected to polyphasic characterization, including 16S rDNA sequence analysis, DNA-DNA hybridizations, biochemical tests, whole-cell protein and fatty-acid analyses. All strains were shown to belong to the Ralstonia branch of the beta-Proteobacteria. Whole-cell protein profiles and DNA-DNA hybridizations revealed two clearly distinct groups, showing low similarity to known Ralstonia species. These two groups, of 8 and 17 isolates, were assigned to two new species, for which the names Ralstonia campinensis sp. nov. and Ralstonia metallidurans sp. nov. are proposed. The type strains are WS2T (= LMG 19282T = CCUG 44526T) and CH34T (= LMG 1195T = DSM 2839T), respectively. Six isolates were allocated to Ralstonia basilensis, which presently contains only the type strain; an emendation of the latter species description is therefore proposed.

Bacterial Proteins↗
PubMed2000

Assessment of electroporation by flow cytometry.

BACKGROUND: Electroporation accomplishes transient permeabilization of cells and thus aids in the uptake of drugs. The method has been employed clinically in the treatment of dermatological tumors with bleomycin. The conditions of electroporation are still largely empirical and information is lacking as to the interrelationships among voltage pulse height, pulse number and toxicity, cell permeation, drug uptake, and effects on drug toxicity. We used propidium iodide (PI) and flow cytometry to define cell permeation into cytoplasmic and nuclear compartments to determine the improvements of drug toxicity that can be accomplished by electroporation. METHODS: Human squamous carcinoma cells of defined TP53 status and normal human epithelial cells were subjected to electroporation using a square wave pulse generator in the range of 0-5,000 V/cm. Flow cytometry served to establish entry of the drug reporter, PI, into the cytoplasm and nucleus. A dye staining method served to establish cell survival and to determine the toxicity of bleomycin alone, electroporation alone, and electroporation with bleomycin. RESULTS: The electric field intensity (EFI) required to produce 50% permeabilization (EP(50)) is cell type dependent. The EP(50) varied from 1,465 to 2,027 V/cm. An EFI below 900 V/cm is growth stimulatory whereas an EFI in excess of 1,000 V/cm is growth inhibitory. An EFI of 1,000 V/cm is sufficient to increase bleomycin toxicity by a factor of 2-3. A differential electroporation efficiency is observed between normal and tumor cells. CONCLUSIONS: Tumor cells can be targeted preferentially at electroporation voltages where normal cells are less permeable.

Antibiotics, Antineoplastic↗
PubMed2000

Effect of venotropic drugs on the respiratory activity of isolated mitochondria and in endothelial cells.

Several drugs used in the treatment of chronic peripheral ischaemic and venous diseases, i.e. aescine, Cyclo 3, Ginkor Fort, hydroxyethylrutosides, naftidrofuryl, naphthoquinone and procyanidolic oligomers, were tested on the mitochondrial respiratory activity. The results show that all these drugs protected human endothelial cells against the hypoxia-induced decrease in ATP content. In addition, they all induced a concentration-dependent increase in respiratory control ratio (RCR) of liver mitochondria pre-incubated with the drugs for 60 min. The drugs were divided into two groups according to their effects. The first group (A), comprising aescine, Ginkor Fort, naftidrofuryl and naphthoquinone, increased RCR by decreasing state 4 respiration rate. The second group of drugs (B), comprising hydroxyethylrutosides, procyanidolic oligomers and Cyclo 3, increased RCR by increasing state 3 respiration rate. The drugs of group A were able to prevent the inhibition of complexes I and III respectively by amytal and antimycin A while the first two drugs of group B increased adenine nucleotide translocase activity. Cyclo 3 inhibited the carbonylcyanide m-chlorophenyl hydrazone (mCCP)-induced uncoupling of mitochondrial respiration. None of these seven drugs could protect complexes IV and V, respectively, from inhibition by cyanide and oligomycin. When tested on endothelial cells the drugs of group A, in contrast to group B, prevented the decrease in ATP content induced by amytal or antimycin A. The present results suggest that the protective effects on mitochondrial respiration activity by these venotropic drugs may explain their protective effect on the cellular ATP content in ischaemic conditions and some of their beneficial therapeutic effect in chronic vascular diseases.

Adenosine Triphosphate↗
PubMed1999

Protection of mitochondrial respiration activity by bilobalide.

Mitochondria alteration is an early event in ischemia-induced damage, and its prevention improves tissue survival upon reperfusion. Adenine translocase and complex I activities are rapidly affected by ischemia. Ginkgo biloba extract demonstrates anti-ischemic properties attributable to the terpenoid fraction, mainly due to the presence of bilobalide. The mechanism of the protection afforded by bilobalide is not yet known. In this work, the effects of bilobalide on mitochondrial respiration were investigated. Mitochondria isolated from rats treated with bilobalide (2 to 8 mg/kg) showed a dose-dependent increase in the respiratory control ratio, due to a lower oxygen consumption during state 4. Bilobalide also decreased the sensitivity of oxygen consumption to inhibition of complex I by Amytal or to inhibition of complex III by antimycin A or myxothiazol. There was no protection of complexes IV and V. It also increased the activity of complex I but not of adenine translocase. Similar effects were also obtained in vitro when control mitochondria were preincubated for 1 hr with 0.8 microg/mL bilobalide. Treatment of the rats with 8 mg/kg bilobalide also prevented the ischemia-induced decrease in state 3 of the mitochondrial respiration and thus the decrease in RCR. The protective effect of bilobalide on cellular ATP content observed under ischemic conditions can be correlated with the above observations. By protecting complex I and III activities, bilobalide allows mitochondria to maintain their respiratory activity under ischemic conditions as long as some oxygen is present, thus delaying the onset of ischemia-induced damage. This mechanism provides a possible explanation for the anti-ischemic properties of bilobalide and of Ginkgo biloba extract in therapeutic interventions.

Animals↗
PubMed1999

Increase in circulating endothelial cells in patients with primary chronic venous insufficiency: protective effect of Ginkor Fort in a randomized double-blind, placebo-controlled clinical trial.

One possible mechanism that accounts for the alterations observed in varicose veins is the activation of endothelial cells by ischemia occurring in the leg veins during blood stasis and the cascade of reactions that follows. Because in vitro data suggest that endothelium alteration is a key event in the development of the pathology, it was important to confirm this hypothesis in patients. We used the number of circulating endothelial cells detached from the vascular wall as a criterion of the endothelium injury. We first compared the number of circulating endothelial cells (CECs) in patients with chronic venous insufficiency (CVI) with those of a control population. A twofold increase in the CEC count (1,001+/-127 CEC/ml of plasma compared with 514+/-82 CECs/ml) was observed in CVI patients, which indeed suggests an alteration of the endothelium in this disease. Second, the protective effect of a venotropic drug, Ginkgo biloba extract, troxerutine, and heptaminol (Ginkor Fort), was tested by a randomized double-blind, placebo-controlled clinical trial. In the active-treatment group, the mean values of the CEC count decreased by 14.5% after a 4-week treatment, whereas in the placebo group, the decrease was less (8.4%). The decrease from week 0 to the end of treatment was significantly higher in the active-treatment group than in the placebo group. These results confirm the important role of the endothelium alterations in the development of varicose veins and suggest a potential beneficial action of a venotropic drug on the venous wall.

Adult↗
PubMed1999

Assignment of Centers for Disease Control group IVc-2 to the genus Ralstonia as Ralstonia paucula sp. nov.

An integrated genotypic and phenotypic analysis of 12 Centers for Disease Control (CDC) group IVc-2 strains revealed that this taxon represents a novel species belonging to the genus Ralstonia. Comparative 16S rDNA sequence analysis allocated a representative CDC group IVc-2 strain to the Ralstonia branch of the beta subclass of the Proteobacteria. DNA-DNA hybridizations did not detect significant binding levels towards any presently known Ralstonia species, including Ralstonia pickettii. Its DNA base ratio is between 65 and 67 mol%. The name Ralstonia paucula sp. nov. is proposed, with strain LMG 3244 (= CDC E6793), isolated from a human respiratory tract, as the type strain. R. paucula can be differentiated from other Ralstonia species by whole-cell protein analysis, amplified rDNA restriction analysis and a variety of classical biochemical tests. Strains have been isolated from various human clinical and environmental sources.

Bacterial Proteins↗
PubMed1999

Effect of Ruscus extract and hesperidin methylchalcone on hypoxia-induced activation of endothelial cells.

BACKGROUND: Ruscus aculeatus extract and the flavonoid hesperidin methylchalcone (HMC) are drugs used in the treatment of chronic venous insufficiency. METHODS: In the present study, we investigated their effects on the activation of endothelial cells by hypoxia, a condition which mimics venous blood stasis. RESULTS: We observed that Ruscus extract was able to inhibit the activation of endothelial cells by hypoxia: the decrease in ATP content, the activation of phospholipase A2 as well as the subsequent increase in neutrophil adherence with a maximal protection obtained at 50 microg/ml. HMC was also able to inhibit the hypoxia-induced decrease in ATP content. Furthermore, the effects of Ruscus extract and of HMC on this decrease seem to be additive. CONCLUSIONS: The biochemical mechanism evidenced in this work might explain some of the beneficial therapeutic effects of these products in the treatment of chronic venous insufficiency patients.

Adenosine Triphosphate↗
PubMed1998

Effect of Ginkor Fort on hypoxia-induced neutrophil adherence to human saphenous vein endothelium.

This study was performed to evaluate the effects of Ginkor Fort, a venotropic drug composed of Ginkgo biloba extract, troxerutine, and heptaminol, on neutrophil adherence to the endothelium of saphenous veins. When saphenous veins were incubated 2 h in hypoxic conditions, they showed a five- to sixfold increase in neutrophil adherence to the endothelium. Ginkor Fort at 0.3 mg/ml was able to inhibit this increase by 69%. These results were confirmed by observations in scanning electron microscopy. Ginkor Fort also inhibited the subsequent activation of these neutrophils, as evidenced by the inhibition of superoxide anion release. The biochemical mechanism of this inhibition of neutrophil adherence was studied on endothelial cells in culture. We observed that Ginkor Fort was able to inhibit the different steps of the activation of endothelial cells by hypoxia: the activation of phospholipase A2 and the decrease in adenosine triphosphate (ATP) content. By preventing the first step of the activation cascade, the decrease in ATP content, Ginkor Fort blocks the subsequent increase in neutrophil adherence as well as neutrophil activation. The biochemical mechanism evidenced in this work might explain the beneficial effect of this drug in the treatment of patients with chronic venous insufficiency.

Cell Adhesion↗
PubMed1997

Perfused human saphenous veins for the study of the origin of varicose veins: role of the endothelium and of hypoxia.

If venous stasis due to blood stagnation has been recognized to be involved in the development of varicose veins, the mechanism linking this situation to the modifications of the venous wall observed in varicoses is still unclear. In order to study this mechanism, human saphenous veins were incubated in normoxic or hypoxic conditions and the interactions between the endothelium and neutrophils were investigated. We observed that many neutrophils adhered to the endothelium of veins incubated in hypoxic conditions rather than in normoxia and that these adherent neutrophils were activated: they released high amounts of superoxide anion and of leukotriene B4. Studies in scanning electron microscopy confirmed the increased neutrophil adherence to the endothelium as well as their activation. These results were then related to the histological observation of varicose veins. These veins show a thickening of the media with extracellular matrix deposit as well as an alteration of the elastic lamina with the presence of smooth muscle cells in the intima. These results are in agreement with in vitro studies on isolated endothelial cells. They all show that hypoxia is able to activate endothelial cells: they release inflammatory mediators and become adhesive for neutrophils which are then activated. These activated leukocytes release free radicals and proteases which are able to degrade the extracellular matrix. In addition, hypoxia-activated endothelial cells secrete growth factors which will trigger smooth muscle cell proliferation and the synthesis of extracellular matrix components. Altogether and because they are frequently repeated, these processes could eventually lead to alterations of the venous wall similar to those observed in varicose veins.

Cell Adhesion↗