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Biomedical subjects

J Peeters

Publications and source records attributed to J Peeters.

At least 19 recordsLinked to original sources

A multiplex PCR to identify porcine mycoplasmas present in broth cultures.

Mycoplasma hyopneumoniae, Mycoplasma hyorhinis and Mycoplasma flocculare can be present in the lungs of pigs at the same time. These three mycoplasma species all require similar growth conditions and can be recovered from clinical samples using the same media. We have developed a multiplex PCR as a helpful tool for rapid differentiation of these three species in the course of isolation. Based on the 16S ribosomal DNA sequences, three different forward primers and a single reverse primer were selected. Each forward primer was compared to available mycoplasma sequences, showing the primers to be specific. The three amplification products observed of 1129 bp (M. hyorhinis), 1000 bp (M. hyopneumoniae) and 754 bp (M. flocculare) were clearly distinguishable on a 1% agarose gel. In addition, no cross-reaction with Mycoplasma hyosynoviae, another porcine mycoplasma, was noted. This multiplex PCR using the proposed set of primers is the first reported assay that allows the simultaneous identification of the different Mycoplasma species isolated from the lungs of pigs.

Animals↗

Theoretical and experimental study of the product branching in the reaction of acetic acid with OH radicals.

The product distribution of the reaction of acetic acid, CH(3)COOH, with hydroxyl radicals, OH, was studied experimentally and theoretically. Mass-spectrometric measurements at 290 K and 2 Torr of He of the CO(2) yield versus the loss of acetic acid yielded a branching fraction of 64 +/- 14% for the abstraction of the acidic hydrogen as follows: CH(3)COOH + OH --> CH(3)COO + H(2)O --> CH(3) + CO(2) + H(2)O. A quantum chemical and theoretical kinetic analysis showed that the abstraction of the acidic hydrogen is enhanced relative to the abstraction of -CH(3) hydrogens because of the formation of a strong pre-reactive H-bonded complex, where the H-bonds are retained in the H-abstraction transition state. The potential energy surface of the reaction is explored in detail, and the reaction products of the individual channels are identified. The theoretical product branching is found to be critically dependent on the energetic and rovibrational differences between the H-abstraction transition states.

Journal Article↗

A potential link between oral status and hearing impairment: preliminary observations.

Some previous studies suggest an association between tooth loss and hearing loss. The aim of this study is to assess the relation between oral status and hearing acuity. Forty-eight patients (mean age: 64.7 years) were allocated to four groups: one was wearing complete dentures in both jaws, another had shortened dental arches, a third had full dental arches in both jaws and the last lacked any occlusal stops (i.e. no occlusal vertical dimension, because of the absence of teeth or occlusal pairs). Audiological testing was performed in a noise-free chamber. Air and bone conduction were checked at different frequencies and the air-bone gap was determined. After correction for age and gender, a difference in air and bone conduction because of the oral status was found for low and for high frequencies while no significant differences were (P < 0.05) found for the air-bone gap. The number of teeth, number of occluding tooth pairs and presence or lack of occlusal vertical dimension, was significantly related to the gradient of hearing loss (P < 0.05). The discrepancy in hearing loss between complete denture wearers and patients without any occlusal vertical dimension, strengthens the hypothesis that it is the lack of the latter that is associated with hearing loss. At what level hearing loss occurs, needs further investigation.

Aged↗

In vitro susceptibilities of Mycoplasma hyopneumoniae field isolates.

The in vitro susceptibilities of 21 Mycoplasma hyopneumoniae field isolates were determined using a broth microdilution technique. One isolate showed acquired resistance to lincomycin, tilmicosin, and tylosin, while five isolates were resistant to flumequine and enrofloxacin. Acquired resistance against these antimicrobials in M. hyopneumoniae field isolates was not reported previously.

Animals↗

The use of polymer-based electrospun nanofibers containing amorphous drug dispersions for the delivery of poorly water-soluble pharmaceuticals.

Electrostatic spinning was applied to the preparation of drug-laden nanofiber for potential use in oral and topical drug delivery. While this technique is in its infancy with regard to pharmaceutical applications, a number of recent publications suggest that it may be of high value in the formulation of poorly water-soluble drugs by combining nanotechnology and solid solution/dispersion methodologies. The purpose of this article is to describe some of these recently published applications. For immediate release oral application, a water-soluble cellulose polymer was selected (i.e., hydroxypropylmethylcellulose, HPMC) while for topical application, a nonbiodegradable, water-insoluble polymer was investigated (i.e., a segmented polyurethane, SPU). Solutions of the polymer and the drugs in appropriate solvents could be spun across various potentials (16-24 kV) generating nanofibers with diameters ranging from 300 to 2000 nm. Dissolution studies found that the non-woven fabrics derived from HPMC and containing itraconazole dissolved over a time course of minutes to hours depending on the formulation used as well as the drug/polymer ratios. Drug release from the SPU samples was dependent on the incorporated drug as well as nanostructure obtained.

Antifungal Agents↗

Evaluation of virulence of Mycoplasma hyopneumoniae field isolates.

The course of enzootic pneumonia, caused by Mycoplasma hyopneumoniae, is strongly influenced by management and housing conditions. Other factors, including differences in virulence between M. hyopneumoniae strains, may also be involved. The aim of this study was to evaluate the virulence of six M. hyopneumoniae field isolates and link it to genetic differences as determined by randomly amplified polymorphic DNA (RAPD) analysis. Ninety, conventional M. hyopneumoniae-free piglets were inoculated intratracheally with the field isolates, a virulent reference strain or sterile culture medium. Animals were examined daily for the presence of disease signs and a respiratory disease score (RDS) was assessed per pig. Twenty-eight days post infection, pigs were euthanized, blood sampled and a lung lesion score was given. Lung samples were processed for histopathology, immunofluorescence testing for M. hyopneumoniae and isolation of M. hyopneumoniae. RAPD analysis was performed on all M. hyopneumoniae strains. Significant differences between isolates were found for the RDS, lung lesion score, histopathology, immunofluorescence and serology. Based on the results of the different parameters, isolates were divided into three "virulence" groups: low, moderately and highly virulent strains. Typically, a 5000 bp RAPD fragment was associated with the highly and moderately virulent strains whereas it was absent in low virulent strains. It was concluded that high variation in virulence exists between M. hyopneumoniae strains isolated from different swine herds. Further studies are required to determine whether the 5000 bp fragment obtained in the RAPD analysis can be used as a virulence marker.

Animals↗

Evaluation of different calorimetric methods to determine the glass transition temperature and molecular mobility below T(g) for amorphous drugs.

The purpose of the present study was to compare different calorimetric methods used to determine the glass transition temperature (T(g)) and to evaluate the relaxation behaviour and hence the stability of amorphous drugs below their T(g). Data showed that the values of the activation energy for the transition of a glass to its super-cooled liquid state qualitatively correlate with the values of the mean molecular relaxation time constant of ketoconazole, itraconazole and miconazole, three structurally related drugs. Estimation of the molecular mobility by activation energy calculation indicated that loperamide was more stable than its two building blocks T263 and R731. It was further shown that the most commonly used approach to determine T(g) (T(g (1/2 c(p))) leads to erroneous values when enthalpy recovery is significant. In this case, an alternative method based on enthalpic considerations leads to results in accordance to basic thermodynamics. Estimation of molecular mobility based on activation energy calculations is therefore considered to be a valuable alternative for the method based on measurement of the extent of relaxation. When enthalpy relaxation is important, the use of T(g 1/2c(p)) leads to an overestimation of the T(g).

Azoles↗

Patterns of Mycoplasma hyopneumoniae infections in Belgian farrow-to-finish pig herds with diverging disease-course.

Patterns of Mycoplasma hyopneumoniae (Mh) infections were investigated in five clinically infected herds and in five herds subclinically infected with Mh. In the clinically infected herds, housing and management conditions were good whereas these conditions were poor in the subclinically infected herds. In each herd, serum antibodies against Mh were detected in pigs of different ages and nasal swabs were taken for Mh detection using nested PCR (nPCR). The percentage of seropositive pigs in the clinically infected herds increased from 8% in pigs of 9 weeks to 52% in pigs of 18 weeks and seroconversion was most shown between 12 and 15 weeks. In the subclinically infected herds, the percentages increased from 2 to 24% and most of the pigs became seropositive between 15 and 18 weeks. The percentage of nPCR positive pigs at 6 weeks was 16 and 0% in the clinically and subclinically infected herds, respectively. The results demonstrate that the seroprevalences were higher in the clinically infected herds and that most of the pigs became infected with Mh at a younger age. It can be concluded that additional factors different from housing and management, like differences among Mh strains, may determine the infection pattern of Mh and the clinical course of the infection.

Animal Husbandry↗

Characterization of glassy itraconazole: a comparative study of its molecular mobility below T(g) with that of structural analogues using MTDSC.

The objective of the present study was to estimate the molecular mobility of glassy itraconazole below the glass transition, in comparison with structural analogues (i.e. miconazole and ketoconazole).Glassy itraconazole and miconazole were prepared by cooling from the melt. The glassy state of the drug was investigated with modulated temperature DSC using the following conditions: amplitude +/-0.212 K, period 40 s, underlying heating rate 2 K/min. The glass transition was determined from the reversing heat flow and occurred at 332.4 (+/-0.5) K and 274.8 (+/-0.4) K for itraconazole and miconazole, respectively. The jump in heat capacity at the glass transition was 303.42 (+/-3.43) J/mol K for itraconazole and 179.35 (+/-0.89) J/mol K for miconazole. The influence of the experimental conditions on the position of the glass transition of itraconazole was investigated by varying the amplitude from +/-0.133 to +/-0.292 K and the period from 25 to 55 s, while the underlying heating rate was kept constant at 2 K/min. Glass transition temperature, T(g), was not significantly influenced by the frequency of the modulation nor by the cooling rate. However, the relaxation enthalpy at the glass transition increased with decreasing cooling rate indicating relaxation during the glass formation process. To estimate the molecular mobility of the glassy materials, annealing experiments were performed from T(g)--10 to T(g)--40 K for periods ranging from 15 min to 16 h. Fitting the extent of relaxation of glassy itraconazole to the Williams--Watts decay function and comparing the obtained values with those of amorphous miconazole and ketoconazole indicated that the molecular mobility is influenced by the complexity of the molecular structure. The more complex the structure, the more stable the amorphous state.

Algorithms↗

Ypel1: a novel nuclear protein that induces an epithelial-like morphology in fibroblasts.

BACKGROUND: Embryonic development depends on the regulation of cell morphology and behaviour to carry out morphogenesis. One example of this is the development of the face, which is constructed from independent blocks of tissue that must grow in a coordinated way and then fuse to form a continuous tissue. RESULTS: We have isolated a novel gene of unknown function from mouse and quail embryos in a search for genes involved in craniofacial development. Sequence analysis of this gene, known as Ypel1, demonstrates a striking level of amino acid conservation between vertebrates and invertebrates but no significant homology with any other characterized genes. Ypel1 is expressed in the ventral half of early embryos including the branchial arches from which the face derives. Ypel1 localizes to the nucleus, and transfection into fibroblasts induces an epithelial-like transition, which is accompanied by alterations to the cytoskeleton and cell adhesion machinery. In addition, human YPEL1 localizes to chromosome 22q11.2, a region associated with a number of syndromes involving malformation of the craniofacial complex. CONCLUSION: These data suggest a role in regulation of cellular morphology and behaviour that is important for development of the craniofacial complex.

Amino Acid Sequence↗

Polymorphisms of the VDR, ER and COLIA1 genes and osteoporotic hip fracture in elderly postmenopausal women.

In view of the reported associations between osteoporosis and polymorphisms of the vitamin D receptor (VDR), collagen Ialpha1 (COLIA1) and estrogen receptor (ER) genes, an association study was performed between VDR, COLLIA1, and ER genotypes and bone mineral density, biochemical markers of bone turnover and hip fracture occurrence in Belgian older postmenopausal women. The gene polymorphisms were evaluated by restriction fragment length polymorphism analyses, using the restriction enzymes BsmI (VDR), AccB7I (COLIA1), and PvuII and XbaI (ER), respectively. As expected, bone mineral density and biochemical analyses demonstrated significant differences between hip fracture patients and elderly controls. However, no significant differences in genotype distributions or allele frequencies were observed between the cases (n = 135, age 78 +/- 9 years) and controls (n = 239, age 76 +/- 4 years) for any of the gene polymorphisms. Stratification of both study populations according to VDR, COLIA1 or ER genotype did not reveal any statistically significant difference in bone density or bone turnover between subgroups with different genotypes. In conclusion, despite its limited statistical power the outcome of this study does not support the hypothesis of a major contribution of the VDR, COLIA1 or ER polymorphisms to explain variations in bone mineral density or bone turnover, or to identify elderly women at risk of osteoporotic hip fracture.

Aged↗

Inferior outcome of cadaveric kidneys preserved for more than 24 hr in histidine-tryptophan-ketoglutarate solution. Leuven Collaborative Group for Transplantation.

BACKGROUND: During recent years, an increasing number of transplant centers within the Eurotransplant organization have used histidine-tryptophan-ketoglutarate (HTK) solution instead of University of Wisconsin (UW) solution as their preferred cold storage solution for abdominal organ preservation. We report on our single-center experience on the outcome of imported kidneys preserved with either HTK or UW solution in relation to the duration of cold ischemia time (CIT). METHODS: Between July 1989 and July 1997, 323 cadaveric kidneys preserved with UW or HTK and imported as a result of an exchange within the Eurotransplant organization were transplanted at our institution. CIT was <24 hr in 216 kidneys (UW: n=174, HTK: n=42) and > or =24 hr in 107 kidneys (UW: n=67, HTK: n=40). Renal functional outcome was evaluated by comparing delayed graft function and initial non-function rates, daily urinary output, the evolution of serum creatinine, and creatinine clearance at 1, 3, 5, 7, and 14 days and at 1, 3, 6 and 12 months, and graft survival at 1 year after transplantation in relation to the type of cold storage solution and CIT < or > or =24 hr. RESULTS: Whereas the incidence of delayed graft function did not differ significantly between kidneys preserved for less than 24 hr in UW (18.6%) or HTK (26.2%), this rate increased to 50% in HTK kidneys compared to 23.9% in UW kidneys when CIT exceeded 24 hr (P=0.006). Mean serum creatinine and creatinine clearance values were better at 1 and 5 days postoperatively in kidneys preserved <24 hr with UW as compared to HTK (P<0.05). After 24 hr of CIT, HTK-preserved kidneys showed an impaired renal function, not only in the immediate postoperative phase but also at 1, 3, 6, and 12 months after transplantation (P<0.05). Graft survival at 1 year was 92.9% in UW vs. 87.5% in HTK kidneys preserved for <24 hr (NS), and 91% vs. 77.4% when CIT exceeded 24 hr (P=0.059). CONCLUSIONS: From these single-center findings, it can be concluded that UW is superior to HTK in kidney preservation, particularly when CIT exceeds 24 hr.

Adenosine↗

Lack of association between osteoarthritis of the hip and gene polymorphisms of VDR, COL1A1, and COL2A1 in postmenopausal women.

OBJECTIVE: To evaluate whether DNA polymorphisms of the VDR (vitamin D receptor), COL1A1 (alpha1 type I collagen), and COL2A1 (alpha1 type II collagen) genes, which have previously been linked to bone mineral density (BMD) and/or osteoarthritis (OA), are also associated with OA of the hip (OAH). METHODS: Genotype frequency distributions were compared between a group of 239 elderly healthy female controls and a group of 75 female OAH patients who underwent total hip replacement. All participants underwent BMD measurements of the total body, lumbar spine, and femoral neck. Mutation detection was done using polymerase chain reaction followed by restriction enzyme digestion. Polymorphisms were detected by digestion with Bsm I for VDR, Acc B7I for COL1A1, and Pvu II for COL2A1. RESULTS: None of the genotype frequency distributions of any of the examined polymorphisms was significantly different between the OAH group and the control group. No significant differences in BMD variables were observed after stratification of the subjects according to the examined genotypes within each study group. CONCLUSION: In Belgian postmenopausal women, the examined polymorphisms of the candidate genes VDR, COL1A1, and COL2A1 do not significantly contribute to an increased prevalence of OAH or to differences in BMD.

Aged↗

MR imaging in retinoblastoma.

We studied the appearance of retinoblastoma on unenhanced and gadolinium-enhanced images and the accuracy of tumour staging with MR imaging. The MR images were obtained in 18 children with retinoblastoma and compared with histopathological findings after enucleation. The MR imaging included T1-weighted and dual-echo T2-weighted images before, and T1-weighted images after, gadopentetate dimeglumine injection. The contrast between tumour and ipsilateral vitreous strongly increased (57 %) after gadolinium on T1-weighted images (p = 0.004). Tumour was strongly hypointense as compared with ipsilateral vitreous in all patients using heavily T2-weighted (TE = 120 ms) images (p = 0.001). The estimated T2 of tumour (mean 96 + 14 ms) did not correlate with histological grading or degree of calcification. Unenhanced T1-weighted MR images rightfully excluded extrascleral growth in 16 of 16 cases, but its presence was confirmed after enucleation in only one of 2 abnormal MR scans. Invasion of the optic nerve behind the cribriform plate was confirmed in 2 of 3 abnormal gadolinium-enhanced MR scans, but also in 1 of the 15 cases in which MR images were normal. The T2-weighted images were useful in assessing retinal detachment. We conclude that heavily T2-weighted images, unenhanced T1-weighted images and gadolinium-enhanced T1-weighted MR images are complementary in characterizing and staging retinoblastoma.

Contrast Media↗