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Biomedical subjects

M Van Dijk

Publications and source records attributed to M Van Dijk.

9 recordsLinked to original sources
PubMed2000

Assessment of preferential T-helper 1 or T-helper 2 induction by low molecular weight compounds using the local lymph node assay in conjunction with RT-PCR and ELISA for interferon-gamma and interleukin-4.

The local lymph node assay (LLNA) is a new and promising test in mice used to identify contact allergens by means of dermal exposure. Experimentally this assay, which comprises a sensitizing phase only, is also used to identify respiratory allergens. Another, experimentally used test in mice to identify allergens is also based on dermal exposure, but comprises both a sensitizing and effector phase. In this latter test, it has been shown that contact allergens preferentially induce a T-helper 1 (TH1) response, whereas respiratory allergens preferentially induce a T-helper 2 (TH2) response. These responses can be discriminated on the basis of cytokine production, such as IFN-gamma, which is produced by TH1 cells, and IL-4, which is produced by TH2 cells. The aim of the study was to establish whether the LLNA was sufficient to not only identify allergens but also mark them as either a contact or a respiratory allergen. To this end, LLNA responses to the contact allergen dinitrochlorobenzene (DNCB) and the respiratory allergen trimellitic anhydride (TMA) were determined using IFN-gamma and IL-4 mRNA expression and production as parameters. Topical application of TMA resulted in a threefold higher lymphocyte proliferation compared to DNCB 3 and 5 days after the first application, while a similar proliferation was found from Day 7 and onward. RT-PCR showed a similar induction of IFN-gamma and IL-4 mRNA expression. While both DNCB and TMA induced IFN-gamma production, TMA but not DNCB induced IL-4 production. Thus, only IL-4 production seemed a suitable parameter to discriminate between the two compounds. In a second study, the respiratory allergens toluene-2,4-diisocyanate (TDI) and phthalic anhydride (PA) were also assayed 7 days after the first application. Topical application of DNCB and PA resulted in a similar lymphocyte proliferation, while application of TMA and TDI resulted in a 1.8-fold higher proliferation. IFN-gamma production was similar for DNCB, TMA, and TDI, and fourfold lower for PA, while IL-4 production was similar for TMA, TDI, and PA, and 24-fold lower for DNCB. In summary, both studies showed induction of IL-4 production by respiratory allergens, with little or no induction by the contact allergen, holding promise for the possibility of identifying respiratory allergens within the LLNA by measuring IL-4 production 7 days after the first application.

Allergens↗
PubMed2000

Augmentation of (pedicle) screws with calcium apatite cement in patients with severe progressive osteoporotic spinal deformities: an innovative technique.

Screw augmentation with calcium apatite cement (CAC) was used in seven patients with a progressive osteoporotic spinal deformity. Thirty-nine spinal segments (64 screws) were augmented: 15 anteriorly (three patients) and 24 posteriorly (five patients). Dorsally, hemilaminectomy was performed at the level of all augmented screws to rule out CAC leakage. Autogenous bone graft was applied in all patients to induce fusion. Screw augmentation failure occurred in only one patient: 1 of the 16 ventral augmented screws (5.5%) was still loose after the augmentation procedure. In three other patients, 4 out of 48 augmented dorsal screws (5.5%) showed CAC leakage at the pedicle corpus vertebra level. Pedicle wall damage was present at two levels, while at two other levels no wall damage was found during visualization. No CAC-related complications were observed perioperatively. No implant migration was observed, and fusion was observed in all cases at follow-up examination performed at a mean of 32 months after surgery.

Adult↗
PubMed2000

UV exposure alters respiratory allergic responses in mice.

We have tested the hypothesis that exposure to ultraviolet light would inhibit T helper-1 (Th1) responses and stimulate T helper-2 (Th2) responses, and that thus in a mouse model of allergic (i.e. extrinsic) asthma (using ovalbumin [OVA] as the allergen) increased symptoms would be observed, while in a model of Th1-dependent occupational asthma (in which picryl chloride is the allergen) decreased symptoms would be observed. Whereas reduced interferon (IFN)-gamma production, decreased inflammatory responses in the airways, and reduced airway reactivity to nonspecific stimuli were observed in UV-preexposed picryl chloride sensitized and challenged mice, the results in the OVA model were less clear. Increased interleukin (IL)-10 production as a result of UV exposure was observed, together with unchanged IL-4 and IFN-gamma. In addition, decreased OVA-specific immunoglobin, IgG1 and IgE, titers were noted, as well as decreased nonspecific airway hyperreactivity. Eosinophilic inflammatory responses were not influenced. The results indicate that UV exposure can have systemic effects that influence ongoing immune responses in the respiratory tract. The effects are not only restricted to immune responses that are predominantly Th1 dependent (i.e. pulmonary delayed-type hypersensitivity and IFN-gamma production in response to picryl chloride) but also to immune response that are predominantly Th2 dependent, i.e. decreased specific IgE titers.

Animals↗
PubMed1999

Free vascularized bone graft in spinal surgery: indications and outcome in eight cases.

In selected spinal deformities the use of a vascularized graft to establish fusion may be considered: compared to a non-vascularized graft it has superior mechanical properties, resulting in greater graft strength and stiffness, and greater effectiveness in facilitating union. Eight patients with a progressive spinal deformity (four cases) and malignancy (four cases) were treated with resection and/or correction and stabilization. To facilitate (multi)level fusion vascularized fibular grafts were used in two cervical and two thoracolumbar deformities. Fibular (two cases) or iliac grafts (two cases) were used in four cases of spinal reconstruction after vertebrectomy for malignancy. In all patients complete incorporation of the graft was obtained within 5 weeks to 8 months postoperatively. Complications occurred in three cases: one patient had a transient laryngeal edema and laryngeal nerve palsy. Another patient had a non-fatal deep vein thrombosis with pulmonary embolisms, successfully treated with anticoagulants. A third patient developed a lung infection and subsequently a deep infection around the dorsal instrumentation; after hardware removal the infection was controlled. At the latest follow-up (mean 30 months, range 24-48 months) six out of eight patients are alive. One patient died 2.5 years after the intervention due to widespread metastases, while another patient died in the postoperative period due to unknown reasons. Vascularized bone graft in spinal surgery facilitates primary mechanical stability and rapid fusion, and it has higher resistance to infection. The variety of applications of a vascularized graft may extend the range of indications for the use of grafts in spinal surgery.

Adolescent↗
PubMed1999

UVB exposure-induced systemic modulation of Th1- and Th2-mediated immune responses.

Exposure to ultraviolet light, especially UVB wavelengths, can impair immune responses in animals and humans. It is remarkable that this immunomodulation is not restricted to the exposed skin but is also found at other sites, i.e. systemic (distant) immunosuppression. A frequently proposed hypothesis is that UVB exposure inhibits, specifically, T helper 1 (Th1)-mediated immune responses. The major reason for this is that contact hypersensitivity (CHS) and delayed-type hypersensitivity (DTH), both Th1-mediated immune responses, are very sensitive to UVB. For this reason these models are frequently used for photoimmunology studies. In the present study, the effects of UVB exposure were investigated in classical models for Th1-mediated immunity, i.e. CHS models in which picrylchloride or oxazolone were used as low-molecular-weight chemical antigens. In these models, CHS responsiveness and cytokines were measured, the latter by both reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The CHS responses to both contact sensitizers (picrylchloride and oxazolone) were suppressed significantly by pre-exposure to repeated suberythemal UVB exposure. Interferon-gamma (IFN-gamma), interleukin (IL)-12 and IL-4, but not IL-10, were detectable in spleen and draining lymph nodes of sensitized BALB/c mice. Repeated UVB exposure prior to sensitization at a distant locus inhibited both IFN-gamma and IL-12 but not IL-4. In BALB/c mice sensitized with ovalbumin (OVA) in the absence of complete Freund's adjuvant, a model for Th2-mediated immunity, OVA-specific serum IgE and cytokine profiles in the spleen were analysed. Sensitization did lead to a significant increase in OVA-specific IgE serum titres. Pre-exposure to UVB resulted in a decreased OVA-specific IgE serum titre. Both RT-PCR and ELISA showed increased levels of IFN-gamma, IL-4 and IL-10 in the spleens of OVA-sensitized mice. The production of IFN-gamma and IL-4 was not affected by UVB pre-exposure. In contrast, the production of IL-10 was significantly increased. This was probably caused by an up-regulation of Th2 cells. It is remarkable that IFN-gamma is significantly suppressed by UVB in Th1-mediated immune reactions but not in Th2-mediated immune reactions where it even appears to increase. IL-10, which is up-regulated by UVB pre-exposure and produced by, among others, Th2 cells, may represent a shift from Th1- to Th2-mediated immune mechanisms. However, IL-10 can also inhibit Th2 responses, which might be the reason for a decreased IgE titre in the Th2 model. From the results of this study it is concluded that UVB exposure prior to sensitization/immunization not only inhibits Th1-mediated but also Th2-mediated immune responses.

Animals↗
PubMed1995

Beta-tubulin genes from the parasitic nematode Haemonchus contortus modulate drug resistance in Caenorhabditis elegans.

Resistance to antimitotic chemotherapeutics in pathogenic nematodes, fungi and mammalian cells is closely associated with structural changes in cytoskeletal beta-tubulin. We investigated the possibility of using the well-characterised free-living nematode Caenorhabditis elegans as a model for studying the mechanism of resistance against benzimidazole (BZ) drugs in the parasitic nematode Haemonchus contortus. Functional analysis of a conserved beta-tubulin isotype (tub-1) mutation near GTP-binding domain II, which is linked to BZ resistance, was carried out in C. elegans by heterologous expression of: (1) parasite BZ-sensitive alleles; (2) BZ-resistant alleles; and (3) in vitro mutagenised beta-tubulin gene constructs. The injected heterologous gene constructs were not only stably maintained, but also expressed as shown by reverse transcriptase-polymerase chain reaction analysis. The degree of BZ drug susceptibility of the transformants was assayed and quantified by incubation with both benomyl and thiabendazol. All H. contortus tub-1 constructs, which encoded Phe at position 200, conferred susceptibility to thiabendazole in BZ-resistant C. elegans ben-1 mutants. In contrast, constructs carrying Tyr200 did not alter the BZ drug phenotype. From these experiments we conclude that: (1) C. elegans can be used as an expression host, since injected parasite genes were biologically active; and (2) the single Phe to Tyr mutation at position 200 in beta-tubulin isotype 1 is the cause of BZ resistance in H. contortus.

Amino Acid Sequence↗
PubMed1988

Transient expression in mammalian cells of the bacterial reporter gene encoding mercuric reductase: effects of various regulatory elements.

The effect of several transcriptional regulatory elements on gene expression in mammalian cells was investigated. As a reporter gene we have used the bacterial gene merA coding for the enzyme mercuric reductase. Several plasmids were constructed with different promoter/enhancer sequences (pSV/E, pSV/L, pMT, pRSV or pAd) at the 5' end and different splicing (small intron of the T antigen of SV40 or the second intron of the rabbit beta-globin gene) and/or polyadenylation signals (AEn, ALn or AR beta Gn) at the 3' end of the merA gene. Expression was measured in five different mammalian cell lines. In COS cells the highest level of expression is obtained with pSV/L and the lowest level with pSV/E. In HeLa, CV-1, Ltk-, and CHO cells merA expression is relatively high, under control of pRSV and pMT and relatively low under control of pSV/L and pAd. The introns studied have a negative effect on the expression of merA. The presence of a polyadenylation signal downstream from the gene is essential for its expression. The three different polyadenylation signals studied give a similar stimulatory effect on the level of expression of the merA gene.

Animals↗
PubMed1984

N-Acetylglutamate in rat liver during foetal development.

N-Acetylglutamate is present in foetal rat liver at 17 days' gestation. The tissue content (approx. 50 nmol/g wet wt.) remains constant during later foetal life. The appearance of N-acetylglutamate does not parallel the developmental pattern of the urea cycle.

Animals↗