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D Bakker

Publications and source records attributed to D Bakker.

At least 37 records · Page 2Linked to original sources
PubMed2000

Paratuberculosis recognized as a problem at last: a review.

This article attempts to review briefly current opinions on Johne's disease, or paratuberculosis, in ruminants caused by Mycobacterium avium subsp. paratuberculosis. Paratuberculosis has been known to be prevalent in domestic livestock, such as cattle, goats, and sheep, for more than a century. Despite this knowledge only minor efforts have been made to control the disease and, with the attention being focussed on the eradication of other diseases, the problem of paratuberculosis has been neglected in most countries in the past decades. However, recent epidemiological surveys performed in Europe showed a high prevalence of paratuberculosis in cattle and sheep, indicating that the situation has become quite alarming. In addition, the possible role of M. avium subsp. paratuberculosis in the aetiology of Crohn's disease in humans is still debated, as discussed in this article. Therefore, there is suddenly a renewed interest in paratuberculosis, and the disease is recognized as a significant problem. As a consequence, there is a need for reliable diagnostic tools for large-scale use to allow the introduction of programmes to control and eventually eradicate the disease. The current status and the possibilities for such programmes are discussed.

Animals↗
PubMed1999

Heat-shock protein-specific T-cell responses in various stages of bovine paratuberculosis.

Bovine paratuberculosis is characterized by a chronic inflammation of the small intestine, caused by infection with Mycobacterium avium ssp. paratuberculosis. Research regarding diagnostic as well as immunopathogenic aspects of paratuberculosis are hampered by the lack of specific antigens. The aim of the present study was to evaluate the potential of mycobacterial heat-shock proteins, as specific antigens, to measure cell-mediated immune responses during various stages of the disease. In a cross-sectional study, peripheral blood mononuclear cells of 179 cows in different stages of M. avium ssp. paratuberculosis infection, vaccinated against paratuberculosis or noninfected, were used to evaluate lymphoproliferative responses to mycobacterial heat-shock protein of 70 kD (HSP70) and 65 kD (HSP65). In addition, lymphoproliferative responses were measured using purified protein derivate (PPD) preparations from M. avium ssp. paratuberculosis, M. avium and M. bovis as antigens. Responses to HSP70 were higher in the vaccinated animals and in asymptomatic animals that shed the organism in their faeces. Compared with these animals, responses were lower in cows with clinical signs of paratuberculosis. Mycobacterial HSP65 induced less prominent responses compared with HSP70, but showed a similar pattern with regard to the stages of disease. Vaccinated and shedding animals also showed the highest responses to PPD derived from M. avium ssp. paratuberculosis (PPD-P). Observations with short-term cell lines raised to PPD-P and to HSP70 indicated that the similarity between those two antigens was not due to the presence of HSP70 in PPD-P. In conclusion, our study indicated that, as for PPD antigens the mycobacterial heat-shock protein-specific cell-mediated immune responses decrease when comparing the asymptomatic stage to the clinical stage in bovine paratuberculosis. Furthermore, this study shows that HSP70, being a well-defined antigen in comparison with PPD antigens, can be used to monitor cell-mediated immune responses in studies regarding the immunopathogenesis of bovine paratuberculosis.

Animals↗
PubMed1999

Perfusion weighted imaging during migraine: spontaneous visual aura and headache.

Using perfusion weighted imaging, we studied 28 spontaneous migraine episodes; 7 during visual aura (n = 6), 7 during the headache phase following visual aura (n = 3), and 14 cases of migraine without aura (n = 13). The data were analyzed using a region-of-interest-based approach. During aura, relative cerebral blood flow (rCBF) was significantly decreased (27% +/- 0.07) in occipital cortex contralateral to the affected hemifield. rCBV was decreased (15% +/- 0.12) and mean transit time increased (32% +/- 0.3), persisting up to 2.5 h into the headache phase. Other brain regions did not show significant perfusion changes. During migraine without aura, no significant hemodynamic changes were observed. In one patient who experienced both migraine with and without aura, perfusion deficits were observed only during migraine with aura. These findings suggest that decremental blood flow changes in occipital lobe are most characteristic of migraine with aura.

Adult↗
PubMed1999

Development of diagnostic reagents to differentiate between Mycobacterium bovis BCG vaccination and M. bovis infection in cattle.

In Great Britain a recent independent scientific review for the government has concluded that the development of a cattle vaccine against Mycobacterium bovis holds the best long-term prospect for tuberculosis control in British herds. A sine qua non for vaccination is the development of a complementary diagnostic test to differentiate between vaccinated animals and those infected with M. bovis so that test-and-slaughter-based control strategies can continue alongside vaccination. In order to assess the feasibility of developing a differential diagnostic test for a live vaccine, we chose M. bovis BCG Pasteur as a model system. Recombinant forms of antigens which are expressed in M. bovis but not, or only at low levels, in BCG Pasteur (ESAT-6, MPB64, MPB70, and MPB83) were produced. These reagents were tested either alone or in combination by using peripheral blood mononuclear cells from M. bovis-infected, BCG-vaccinated, and Mycobacterium avium-sensitized calves. All four antigens induced in vitro proliferation and gamma interferon responses only in M. bovis-infected animals. A cocktail composed of ESAT-6, MPB64, and MPB83 identified infected animals but not those vaccinated with BCG. In addition, promiscuous T-cell epitopes of ESAT-6, MPB64, and MPB83 were formulated into a peptide cocktail. In T-cell assays with this peptide cocktail, infected animals were identified with frequencies similar to those obtained in assays with the protein cocktail, while BCG-vaccinated or M. avium-sensitized animals did not respond. In summary, our results suggest that peptide and protein cocktails can be designed to discriminate between M. bovis infection and BCG vaccination.

Amino Acid Sequence↗
PubMed1999

Prevalence of Mycobacterium avium in slaughter pigs in The Netherlands and comparison of IS1245 restriction fragment length polymorphism patterns of porcine and human isolates.

A significant increase in the incidence of caseous lesions in the lymph nodes of slaughter pigs prompted a large-scale investigation in five slaughterhouses in The Netherlands. In total, 158,763 pigs from 2,899 groups underwent gross examination. At least one pig with caseous lesions in the submaxillary and/or mesenteric lymph nodes was observed in each of 154 of the 2,899 groups examined (5%). In total, 856 pigs (0.5%) were affected. As many as five pigs in each of 141 of the 154 positive groups (91.5%) had lymph node lesions. Greater numbers of pigs with affected lymph nodes were found in 13 groups (8.5%). Four pigs had lesions in the kidneys, liver, or spleen. Acid-fast bacteria were detected by microscopic examination of 121 of 292 Ziehl-Neelsen-stained smears of caseous lesions (41%). In a follow-up study, Mycobacterium avium complex (MAC) bacteria were isolated from 219 of 402 affected lymph nodes (54.2%). Ninety-one of the isolated strains were analyzed by restriction fragment length polymorphism (RFLP) typing with insertion sequence IS1245 as a probe. All but 1 of these 91 strains contained IS1245 DNA, indicating that pigs in The Netherlands carried almost exclusively M. avium bacteria and no other bacteria of MAC. Only one pig isolate exhibited the bird-type RFLP pattern. MAC isolates from 191 human patients in The Netherlands in 1996 were also typed by RFLP analysis. Computer-assisted analysis showed that the RFLP patterns of 61% of the human isolates and 59% of the porcine isolates were at least 75% similar to the RFLP patterns of the other group of strains. This indicates that pigs may be an important vehicle for M. avium infections in humans or that pigs and humans share common sources of infection.

Animals↗
PubMed1999

Important issues in clinical practice: perspectives of oncology nurses.

As the 1990's draw to a close, the cancer care environment is undergoing rapid change. Many issues exist within the complex environment of cancer care that could create a challenge in providing quality nursing care to patients. This study examined the current challenges oncology nurses face in their daily practice. Surveys were mailed to members of the Canadian Association of Nurses in Oncology asking them to indicate on a list of 80 issues which were problems in their daily practice. From the responses of 249 oncology nurses, the following items were ranked as the top 10 problems: anxiety, coping/stress management, bereavement/death, fatigue, metastatic disease, comfort, pain control and management, quality of life, recurrence of primary cancer, and nurse burn-out. Principal component analysis was conducted to determine if patterns existed in the way problems had been rated. Five components explained 42% of the variance in the data set: comprehensive cancer care, communication, experience of loss, terminal illness, and signs and symptoms. Implications for nursing practice, education and research are highlighted.

Adaptation, Psychological↗
PubMed1998

Polyacids as bonding agents in hydroxyapatite polyester-ether (Polyactive 30/70) composites.

A previously developed method to improve the interface between hydroxyapatite (HA) and a polyester-ether (Polyactive 70/30) by using polyacrylic acid or poly(ethylene-co-maleic acid) has been applied to HA/Polyactive 30/70 composites noting that polyactive 30/70 contains less polyethylene glycol (PEG) segments and a higher concentration of rigid poly(butylene terephthalate) (PBT) segments. The mobility of the PEG segments is significantly affected by the existence of a high concentration of rigid PBT segments. Our experimental results show that this method is indeed suitable for making HA/Polyactive 30/70 composites. The hydrogen bond/dipole interaction forming ability of the PEG segment is not affected by the existence of relatively large amounts of PBT segments. By using these coupling agents, the mechanical properties of the composite can be significantly improved both in dry and wet states. A fractographical study of the fracture surfaces revealed that the surface modified HA particles maintain better contact at fracture. It also showed that larger HA particles may initiate cracks and that such particles may be responsible for a decrease in the tensile strength of the composites.

Journal Article↗
PubMed1998

The F41 adhesin of enterotoxigenic Escherichia coli: inhibition of adhesion by monoclonal antibodies.

The anti-adhesive properties of 23 specific monoclonal antibodies (MAbs) against the F41 adhesive fimbrial antigen of enterotoxigenic Escherichia coli (ETEC) were studied in brush border adhesion inhibition tests and haemag-glutination inhibition tests with four F41-positive E. coli strains and purified F41 antigen. These MAbs recognize five epitope clusters, F41-1 to F41-5. It was proven that these epitope clusters were located on the 29 kDa F41 major fimbrial subunits. All nine MAbs against epitope cluster 1 inhibited the adhesion of F41-positive strains to brush border preparations of calf and pig intestines and the haemagglutination of sheep and guinea pig erythrocytes by the F41-positive strains and purified F41 antigen. The fourteen MAbs against the other four epitope clusters showed very little to no blocking of adhesion and haemagglutination. The results indicate that the adhesion of F41 to intestinal epithelial cells is mediated by the same domain of the 29 kDa F41 major fimbrial subunit(s) as the adhesion of F41 to erythrocytes. Irrespective of their epitope specificity F41 MAbs protected infant mice against a challenge with F41-positive ETEC. MAbs against all epitope clusters partly protected piglets against challenge with F41-positive ETEC in a similar way. Therefore, we conclude that direct blocking of the receptor binding site located on the major fimbrial subunit is not the main mechanism how antibodies protect against ETEC infection.

Adhesins, Escherichia coli↗
PubMed1998

Commitment of a cancer organization to a program for training in communication skills.

An Ontario cancer agency started an initiative to improve and promote effective communications between health care providers and their patients, using a 4.5-hour workshop developed by the Bayer Institute for Health Care Communications. Each of the eight regional cancer centers in Ontario sent two people, one physician and one other health care professional, for training in delivery of the workshop. Subsequently, each center provided workshops for physicians, nurses, pharmacists, physicists, social workers, psychologists, radiotherapists, and secretarial staff. The ongoing workshops are multiprofessional in composition and interactive and participatory in design. Between September 1996 and September 1997, the workshops involved over 400 cancer care professionals. Their success has been attributed to the knowledge, skills, and enthusiasm of the trained pair of facilitators; the interactive and participatory nature of the workshop design; the multiprofessional participation; and the support of the board of directors and senior management and the administration of each cancer center.

Communication↗
PubMed1997

Deterioration of visual fields in patients with glaucoma with and without optic disc hemorrhages.

OBJECTIVE: To evaluate visual field deterioration in patients with glaucoma with and without optic disc hemorrhages (DHs). DESIGN: A prospective study at quarterly base involving annual perimetry; mean follow-up of 9 years. SETTING: Outpatient department, nonreferral basis. PATIENTS: Sixty-eight patients with primary open-angle glaucoma, 34 with normal pressure glaucoma (NPG), and 125 with ocular hypertension. RESULTS: Visual field deterioration occurred in 32%, 32%, and 6% of the patients without DHs who had NPG, primary open-angle glaucoma, or ocular hypertension, respectively, while visual field deterioration occurred in 80%, 89%, and 14% of patients with DH, respectively. Cox proportional hazards ratio(CHR) for deterioration in patients with vs patients without DHs was 5.4 for NPG (P<.01) and 3.6 for primary open-angle glaucoma (P<.01). In patients with NPG and DHs, ipsilateral eyes with DHs deteriorated in 58%, while contralateral eyes without DHs deteriorated in 11% (CHR, 8.9; P<.04). For primary open-angle glaucoma and ocular hypertension, progression did not differ between eyes with DHs and contralateral eyes without DHs. Mean (+/-SD) interval between DHs and ipsilateral visual field deterioration was 3.1+/-1.7 years. No difference in the proportion of eyes progressing after single or recurrent DHs was noted. The position of DHs was related to the site of the visual field loss in 44% of the eyes. CONCLUSIONS: The presence of DHs increased the risk of visual field deterioration. Disc hemorrhages were indicative only of deterioration in ipsilateral eyes in patients with NPG.

Disease Progression↗
PubMed1997

Spontaneous eye blinking, a measure of dopaminergic function, in children with acquired immunodeficiency syndrome.

OBJECTIVE: To investigate possible alterations in dopaminergic function in children with acquired immunodeficiency syndrome by evaluating spontaneous eye blink rate, a putative measure of central dopaminergic function. DESIGN: Evaluation of previously videotaped test sessions of a consecutive case series of 50 children (mean age, 5.2 years; range, 2-12 years) with acquired immunodeficiency syndrome. SETTING: Government medical research center. RESULTS: Intrarater reliability was high, expected co-variation of blink rate with age and concurrent mental activity were confirmed, and obtained rates were similar to published data. Higher blink rates, suggestive of increased dopaminergic function, were associated with more severe cortical atrophy (P < .05) and white matter abnormality (P < .05) on computed tomographic brain scans. The presence or severity of basal ganglia calcifications did not seem to influence blink rate. In addition, higher blink rates were associated with higher ratings of depressed affect (P < .05) and lower ratings of hyperactive behaviors (P < .05) during other test activities. CONCLUSIONS: The higher blink rates in human immunodeficiency virus-infected children with more severe cortical abnormalities suggest increased central dopamine activity compared with that in children without cortical computed tomographic brain scan abnormalities. Thus, as a result of structural brain abnormalities, neurotransmitter levels in children with acquired immunodeficiency syndrome may vary and this may be reflected in their socioemotional functioning.

AIDS Dementia Complex↗
PubMed1997

The bone-bonding polymer Polyactive 80/20 induces hydroxycarbonate apatite formation in vitro.

The bone-bonding polymer known as Polyactive is a block copolymer composed of a polyethylene oxide (PEO) soft segment and a polybutylene terephthalate (PBT) hard segment. This study focuses on the in vitro induction of hydroxyapatite by Polyactive. Our results show that Polyactive is capable of inducing hydroxycarbonate apatite (HCAp) formation from a metastable calcium phosphate solution analogous to a physiological solution. In a 4-day incubation, the HCAp formation extended approximately 100 microm deep from the surface. A great number of globules about 1 microm large were found in the calcified Polyactive. These globules were composed of HCAp crystals embedded in the polymer matrix. There were so many globules in the surface that they connected with each other and formed a calcified layer. Next to the calcified layer was a zone where the globules were scattered. The calcified surface may have acted to promote HCAp growth from the solution, bringing about the formation of a HCAp layer on top of the calcified layer. The transition of solid Polyactive into a Polyactive hydrogel in calcium phosphate solution permitted HCAp formation within the polymer. It is proposed that the COOH groups produced during hydrolysis of Polyactive play an important role in nucleating hydroxyapatite. A remarkable affinity of the PEO segment of the polymer for calcium ions may facilitate moving calcium and phosphate from the solution into the polymer for the growth of HCAp.

Biocompatible Materials↗
PubMed1996

Femoral canal occlusion in total hip replacement using a resorbable and flexible cement restrictor.

We have investigated the use of a conically-shaped cement plug made of Polyactive (PA), a biodegradable copolymer. The flexibility and hydrogel properties were thought to facilitate occlusion of the femoral canal even when it was oval or irregular in shape. The function of the plug was first compared with that of the Thackray polyethylene model in 16 artificial plastic femora. The maximum intramedullary pressure achieved during cementing was ten times higher with the biodegradable model. Migration or leakage of cement did not occur when the diameter of the femoral canal was equal to or smaller than the diameter of the plug. We also showed that the biodegradable properties of this implant were such that it did not require removal during revision. The new plug was tested in a pilot clinical trial. At two years only two out of 21 patients had evidence of migration or leakage of cement, probably due to a mismatch in the size of plug and femoral canal. There were no local changes in the femur.

Biocompatible Materials↗
PubMed1994

Leucine-responsive regulatory protein, IS1 insertions, and the negative regulator FaeA control the expression of the fae (K88) operon in Escherichia coli.

Nucleotide sequence analysis of the fae operon encoding the biosynthesis of K88 fimbriae revealed the presence of two divergently transcribed regulatory genes, faeA and faeB, separated by two inverted IS1 insertions. The amino acid sequences of the regulatory proteins FaeA and FaeB show similarity to the primary structure of corresponding regulatory proteins involved in the biosynthesis of Pap and S fimbriae. Expression of faeA is positively controlled by the FaeA protein, whereas K88 fimbriae production is negatively controlled by the co-operative activity of FaeA and the leucine-responsive regulatory protein (Lrp). Exchange of FaeA for Papl, a positive regulator of Pap fimbriae expression, also represses K88 production indicating that the combination Papl/Lrp has opposite effects on fae and pap expression. Mutations in faeB had no effect on the biosynthesis of K88 fimbriae. The presence of the two IS1 insertions is hypothesized to neutralize part of the repression of K88 biosynthesis by FaeA/Lrp. Like pap, the fae operon does not respond to exogenous leucine.

Amino Acid Sequence↗