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Biomedical subjects

J de Groot

Publications and source records attributed to J de Groot.

At least 19 recordsLinked to original sources
PubMed2001

Induction of tolerance and cross-tolerance to methacrylate contact sensitizers.

Induction of immunological tolerance to contact allergens might prevent undesired sensitization, in particular to occupational sensitizers, e.g., methacrylates (MA). Here, using a guinea pig model, we studied to which extent tolerance to one methacrylate might result in cross-tolerance to other congeners. Strong tolerance to the monomethacrylates hydroxy-ethyl MA (HEMA) and methyl MA, but not to the dimethacrylate ethylene-glycol MA (EGDMA) could be induced. The induced tolerance was stable, could not be broken by repeated sensitization attempts, and was mediated by specific suppressor cells, as demonstrated in T cell transfer experiments. In HEMA-tolerized animals, strong cross-tolerance to methacrylate congeners, including EGDMA, itself being nontolerogenic and showing the lowest cross-reactivity to HEMA, was found. Thus, oral application of contact allergens, to which skin contact cannot be avoided, e.g., in occupational settings, can induce broad cross-tolerance to related substances and might offer a promising preventive approach.

Allergens↗
PubMed2001

Long-term effects of social stress on antiviral immunity in pigs.

Mixing of unfamiliar pigs is common practice in intensive pig husbandry. Since pigs maintain a dominance hierarchy, mixing often leads to vigorous fighting. Apart from the negative impact that fighting has on welfare, there is evidence that the social stress associated with fighting suppresses immune function. In the present experiment, we investigated the impact of mixing on specific long-term immune responses and protection against challenge infection after vaccination with pseudorabies virus (PRV). Specific pathogen-free (SPF) pigs were mixed pairwise with an unfamiliar same-gender conspecific or left undisturbed with a same-gender littermate at 3 days after vaccination with PRV. Half of the pigs were females (gilts) and half were castrated males (barrows). Mixing increased agonistic behavior to the same degree in gilts and barrows. Cortisol concentrations in saliva and catecholamine excretion in urine were increased in mixed pigs, and these effects were independent of dominance status and gender. Subsequently, the effects of mixing, gender, dominance status and interactions between these factors on immune response parameters were studied. The main result was that mixed barrows showed suppressed immune responses after vaccination and increased clinical symptoms after challenge infection compared to control barrows. Mixed gilts however did not differ from control gilts. It also appeared that mixed dominants were more seriously affected than mixed subordinates were. We conclude that, in some pigs, social stress after mixing suppresses the immune response to a viral vaccine and consequently impairs protection against challenge infection.

Agonistic Behavior↗
PubMed2001

Biomonitoring the intake of garlic via urinary excretion of allyl mercapturic acid.

Allium vegetables (onions, leeks, chives) and in particular garlic have been claimed to have health-promoting potential. This study was conducted to get insight into the perspectives for monitoring the intake of garlic by a biomarker approach. Chemically, the biomarker results from exposure to gamma-glutamyl-S-allyl-l-cysteine, which is first hydrolysed by gamma-glutamine-transpeptidase resulting in the formation of S-allyl-l-cysteine. The latter compound is subsequently N-acetylated by N-acetyltransferase into S-allyl-mercapturic acid (ALMA) and excreted into urine. The mercapturic acid was measured in urine using gaschromatography with mass spectrometry. Thus the intake of garlic was determined to check the compliance of garlic intake in a placebo-controlled intervention study. Results indicate that S-allyl-mercapturic acid could be detected in 15 out of 16 urine samples of garlic supplement takers, indicating good compliance. In addition, the intake of garlic was also monitored in a cross-section study of vegans versus controls in Finland, in which no differences in garlic consumption nor in ALMA output were recorded between vegans and controls. These data indicate good possibilities for further studies in the field of biomarkers to investigate the putative chemopreventive effects of garlic and garlic-containing products.

Acetylcysteine↗
PubMed2001

Developing a training program to improve supervisor-resident relationships, step 1: defining the types of issues.

BACKGROUND: By some estimates, the teacher-learner relationship explains roughly half of the variance attributed to the effectiveness of teaching. Despite this, relationships largely have been ignored in the educational literature. PURPOSE: This qualitative pilot study sought to identify factors in the supervisor-resident relationship that hinder learning among University of Toronto psychiatry residents. METHOD: Thirteen postgraduate-year residents in Years 2-5 and their supervisors were interviewed regarding interactions that either assisted or adversely affected learning. RESULTS: Qualitative analysis of the interview data led to the identification of 5 types of issues affecting the supervisory relationship: goals and individual differences, communication and feedback, power and rivalry, support and collegiality, and role modeling and expertise. Face validity was supported when typed anonymous written feedback obtained from annual supervisor evaluations also could be organized into the 5 categories. CONCLUSIONS: Recognition of the types of interpersonal interactions that assist or hinder learning may contribute to enhanced teaching effectiveness.

Canada↗
PubMed2001

The developmental profile.

We describe the Developmental Profile and the development of the instrument, the theory on which it is based, and the manner in which information is collected, interpreted, and used in clinical practice. We present the results of the psychometric research that has been performed to date. Finally, we examine the extent to which this method is in accordance with recent insights within the field of personality diagnostics.

Freudian Theory↗
PubMed2001

Mild isolation procedure discloses new protein structural properties of beta-lactoglobulin.

To explore the potentially available functional properties of beta-lactoglobulin in, for example, the processing of food products, it is important to isolate the protein by a procedure that avoids all possible denaturing conditions, such as low pH, high ionic strength, or low or elevated temperatures that could cause the protein to undergo irreversible conformational changes. In this work, a mild isolation protocol for beta-lactoglobulin from bovine milk is presented, applicable to semi large-scale isolations (50 to 200 g). The protein could be isolated with a high efficiency (>80%) and a good purity (>98%). Biochemical characterization of the material demonstrated no lactosylation of the protein, nor the formation of irreversibly associated dimers. Also, no proteose peptones could be detected. The ability of beta-lactoglobulin to undergo conformational changes is studied by far and near-ultraviolet circular dichroism and differential scanning calorimetry. A "global" unfolding of the protein is detected around 72 (tertiary level) and 77 degrees C (secondary level). The dimer-monomer dissociation occurring around 52 degrees C could also be monitored at a secondary structural level. Remarkably, a low temperature transition around 30 degrees C was observed, where approximately 10 beta-stranded residues unfold cooperatively, not been reported previously. This low temperature transition is irreversible at temperatures higher than 35 degrees C or upon freezing the material at -20 degrees C. The addition of 20% glycerol could prevent this irreversible conformational change. The effect of the low temperature transition on the protein's functionality remains to be investigated.

Animals↗
PubMed2000

The Fanconi anemia protein FANCF forms a nuclear complex with FANCA, FANCC and FANCG.

Fanconi anemia (FA) is a chromosomal instability syndrome associated with a strong predisposition to cancer, particularly acute myeloid leukemia and squamous cell carcinoma. At the cellular level, FA is characterized by spontaneous chromosomal breakage and a unique hypersensitivity to DNA cross-linking agents. Complementation analysis has indicated that at least seven distinct genes are involved in the pathogenesis of FA. Despite the identification of four of these genes (FANCA, FANCC, FANCF and FANCG), the nature of the 'FA pathway' has remained enigmatic, as the FA proteins lack sequence homologies or motifs that could point to a molecular function. To further define this pathway, we studied the subcellular localizations and mutual interactions of the FA proteins, including the recently identified FANCF protein, in human lymphoblasts. FANCF was found predominantly in the nucleus, where it complexes with FANCA, FANCC and FANCG. These interactions were detected in wild-type and FA-D lymphoblasts, but not in lymphoblasts of other FA complementation groups. This implies that each of the FA proteins, except FANCD, is required for these complexes to form. Similarly, we show that the interaction between FANCA and FANCC is restricted to wild-type and FA-D cells. Furthermore, we document the subcellular localization of FANCA and the FANCA/FANCG complex in all FA complementation groups. Our results, along with published data, culminate in a model in which a multi-protein FA complex serves a nuclear function to maintain genomic integrity.

Antibody Specificity↗
PubMed2000

Cloning and characterization of murine fanconi anemia group A gene: Fanca protein is expressed in lymphoid tissues, testis, and ovary.

Fanconi anemia (FA) is an autosomal recessive disorder in humans characterized by bone marrow failure, cancer predisposition, and cellular hypersensitivity to cross-linking agents such as mitomycin C and diepoxybutane. FA genes display a caretaker function essential for maintenance of genomic integrity. We have cloned the murine homolog of FANCA, the gene mutated in the major FA complementation group (FA-A). The full-length mouse Fanca cDNA consists of 4503 bp and encodes a protein with a predicted molecular weight of 161 kDa. The deduced Fanca mouse protein shares 81% amino acid sequence similarity and 66% identity with the human protein. The nuclear localization signal and partial leucine zipper consensus motifs found in the human FANCA protein were also present in the murine homolog. In spite of the species difference, the murine Fanca cDNA was capable of correcting the cross-linker sensitive phenotype of human FA-A cells, suggesting functional conservation. Based on Northern as well as Western blots, Fanca was mainly expressed in lymphoid tissues, testis, and ovary. This expression pattern correlates with some of the clinical symptoms observed in FA patients. The availability of the murine Fanca cDNA now allows the gene to be studied in experimental mouse models.

Amino Acid Sequence↗
PubMed1999

A physical complex of the Fanconi anemia proteins FANCG/XRCC9 and FANCA.

Fanconi anemia (FA) is a recessively inherited disease characterized at the cellular level by spontaneous chromosomal instability and specific hypersensitivity to cross-linking agents. FA is genetically heterogeneous, comprising at least eight complementation groups (A-H). We report that the protein encoded by the gene mutated in complementation group G (FANCG) localizes to the cytoplasm and nucleus of the cell and assembles in a molecular complex with the FANCA protein, both in vivo and in vitro. Endogenous FANCA/FANCG complex was detected in both non-FA cells and in FA cells from groups D and E. By contrast, no complex was detected in specific cell lines belonging to groups A and G, whereas reduced levels were found in cells from groups B, C, F, and H. Wild-type levels of FANCA/FANCG complex were restored upon correction of the cellular phenotype by transfection or cell fusion experiments, suggesting that this complex is of functional significance in the FA pathway. These results indicate that the cellular FA phenotype can be connected to three biochemical subtypes based on the levels of FANCA/FANCG complex. Disruption of the complex may provide an experimental strategy for chemosensitization of neoplastic cells.

Cell Fusion↗
PubMed1999

A single social defeat transiently suppresses the anti-viral immune response in mice.

Most of the studies dealing with effects of stress on anti-viral immunity have been carried out with stressors that are of long duration and that bear little relationship to the nature of the species. In this paper, we investigated the effect of a stressor mimicking real-life situations more closely, being social defeat of male mice, on anti-viral immunity. A single social defeat was applied at 3 or 6 days after inoculation with pseudorabies virus, a herpes virus. It appeared that lymph node cellularity, virus specific IL-2 and IFN-gamma production and lymphocyte proliferation were suppressed at 1 day after defeat, but these parameters restored to control values quickly thereafter. We conclude that the stress of a single social defeat evokes a transient immune suppression, which might have consequences if a pathogenic or lethal virus is involved.

Animals↗
PubMed1999

Effects of mild stress on the immune response against pseudorabies virus in mice.

Stress is a recognised problem in intensive pig husbandry, which might lead to changes in immune reactivity. To study the effect of stress on the development of an anti-viral immune response, we used a murine model in which mice were immunized with an attenuated strain of pseudorabies virus (PRV). The effect of two stress treatments, both relevant to intensive pig husbandry, on the development of the specific immune response against PRV was investigated. The stress treatments consisted of restraint, social isolation, and transport and they differed in predictability. The specific immune response against PRV, which developed in the draining lymph nodes, was measured by a lymphocyte proliferation assay and cytokine production assays. Our results showed that the unpredictable stress treatment had no effect on the development of the immune response against PRV in mice, whereas the predictable stress treatment actually hastened the immune response.

Animals↗
PubMed1998

Cross-reactivity patterns of contact-sensitizing methacrylates.

Methacrylates are well-known contact sensitizers with increasing frequency of contact leading to occupational skin disease. Here, we developed an animal model to facilitate studies on the sensitizing capacities and cross-reactivity patterns between four clinically most important allergens: methacrylate (MMA), 2-hydroxyethyl methacrylate (2-HEMA), 2-hydroxypropyl methacrylate (2-HPMA) and ethyleneglycol dimethacrylate (EGDMA). Inbred guinea pigs were immunized by ic injections of 300 microliters of 1.0 M methacrylate solutions in Freund's complete adjuvant into both flanks, both ears, and the neck. After 14 days open skin tests were performed with 50% MMA, 2-HEMA, or 2-HPMA or 10% EGDMA solutions in 40% DMSO in ethanol. Cross-reactivities were investigated 14 days later by skin testing with all four methacrylates. Using this newly developed protocol, strongly positive skin tests for methacrylates could be induced in almost all guinea pigs (MMA 26/26, 2-HEMA 16/18, 2-HPMA 15/16 and EGDMA 11/11). Whereas EGDMA induced only weak or infrequent cross-reactivities, 2-HEMA sensitization led to strong cross-reactions to all other methacrylates. Both MMA and 2-HPMA induced strong cross-reactivity to EGDMA but only weak to moderate reactivities to the other methacrylates. The absence of strong cross-reactions with monomethacrylates in EGDMA (dimethacrylate)-sensitized animals may be explained by the predominance of highly EGDMA-specific T-cells in these animals. In contrast, sensitization with MMA, 2-HEMA, and 2-HPMA would lead to recruitment of T-cells cross-reactive to the other monomethacrylates, according to their molecular similarities. The strong skin hypersensitivities observed for EGDMA in these latter groups are ascribed to enzymatic degradation into monomethacrylate compounds, notably 2-HEMA, at a rate sufficient to elicit cognate effector T-cells. The results of this study offer new insights in the development of methacrylate hypersensitivities and common cross-sensitization patterns in clinical practice.

Allergens↗
PubMed1998

Coming alive: the psychotherapeutic treatment of patients with eating disorders.

OBJECTIVE: To describe a dynamic psychotherapeutic approach specifically developed for women with eating disorders. METHOD: The developmental origins and psychological disturbances associated with eating disorders are outlined based on a review of the literature and the authors' observations. Principles from contemporary psychodynamic theories that focus on subjectivity and intersubjectivity are applied to the treatment of women with eating disorders and are illustrated with clinical vignettes. Theoretical models employed include intersubjective and relational theory, self psychology, and feminist psychodynamic theory. RESULTS: Relative unresponsiveness to a child's subjective experience and to child-initiated cues are thought to contribute to psychological disturbances among women with eating disorders. These disturbances include impairment in the sense of effectiveness, in the capacity to appreciate and tolerate emotions, and in the continuity and cohesiveness of self-experience. Self-imposed starvation, binge-purge episodes, and excessive exercise may act as psychic organizers in women with these vulnerabilities. An active psychotherapeutic approach with sustained interest in the patient's authentic subjective experience promotes the identification, organization, and integration of emotional experience and the consolidation of a more differentiated sense of self. CONCLUSION: In the psychotherapeutic treatment of women with eating disorders, a therapeutic posture of sustained empathic enquiry contributes to the patient's curiosity about her own subjective world. Feeling understood in a therapeutic relationship and feeling assisted in organizing and understanding one's subjective experience contributes to the gradual unfolding of the psychological sense of self.

Adult↗
PubMed1996

Reversal of orally induced T-cell tolerance by subcutaneous administration of interleukin-12 at the site of attempted sensitization.

Feeding of proteins causes peripheral T-cell tolerance, as revealed by reduced delayed-type hypersensitivity (DTH) reactivity after immunization. Using ovalbumin-fed mice, we studied whether putatively immunostimulatory cytokines could reverse this state of mucosal tolerance. It was found that local administration of neither IL-2, IFN-gamma, nor GM-CSF resulted in reversal of tolerance. In contrast, subcutaneous administration of IL-12 at the site of attempted immunization resulted in complete recovery of DTH reactivity. The dichotomy between the two Th1-stimulatory cytokines IFN-gamma and IL-12 was also reflected by different effects on ovalbumin-specific antibody isotypes. Although both IFN-gamma and IL-12 downregulated serum IgG1-levels in tolerant mice, suggesting decreased ovalbumin-specific Th2 function, only local administration of IL-12 led to increased serum Th1-related IgG2a levels. These results support the view that potentiation of Th1 effector function is critical for reversal of mucosal tolerance.

Adjuvants, Immunologic↗
PubMed1996

[Heart diseases in foals. A literature review exemplified by 2 case reports].

A review of the congenital and acquired heart diseases of foals is given on the basis of two patients. A 3-month-old foal with a history of collapse after exercise had a systolic murmur on all heart valves on both sides. Necropsy revealed endocarditis ulcerosa of the left atrioventricular valves. A 6-week-old foal with systolic murmur on the left atrioventricular valves and on the aorta showed, on ultrasonography, signs of endocarditis of the atrioventricular valves. This foal recovered after a long course of antibiotics.

Animals↗
PubMed1994

[Little difference in quality of life of dialysis patients in Utrecht and Willemstad].

OBJECTIVE: To assess and compare the quality of life of patients treated with haemodialysis and chronic ambulatory peritoneal dialysis (CAPD) in Utrecht and Willemstad, Curaçao. DESIGN: Transverse multicentre study. METHODS: All haemodialysis and CAPD patients in Utrecht and all haemodialysis patients in Curaçao under treatment for over 6 months were studied. The objective tests applied were the 'Nottingham health profile', the 'affect balance scale', the 'index of well-being' and the 'Amsterdam complaint profile'. Possible correlations between individual patient-related and treatment-related factors and biochemical variables were also investigated. RESULTS: The objective and subjective tests revealed only slight differences in quality of life in the three groups. In a few respects, the CAPD patients rated the quality of life slightly better. In the Utrecht group a positive relationship was seen between haematocrit (higher owing to treatment with erythropoietin) and plasma bicarbonate concentration, and the quality of life.

Cross-Cultural Comparison↗