Biomedical subjects

C de Ruiter

Publications and source records attributed to C de Ruiter.

At least 19 recordsLinked to original sources

PubMed2000

Personality disorders in a Dutch forensic psychiatric sample: convergence of interview and self-report measures.

Convergence of PDQ-R- and SIDP-R-derived personality disorder diagnoses was studied in a sample of 85 forensic psychiatric patients. For categorical diagnoses, the mean kappa was .34, but on a dimensional level convergence was somewhat higher. Paranoid, antisocial and borderline personality disorders had prevalence rates around 40%; the other personality disorders occurred with much lower frequency. The PDQ-R yielded more diagnoses, except for antisocial, histrionic, narcissistic, and sadistic personality disorder. Because the latter disorders are among the most prevalent in forensic settings, and because they have important risk and treatment implications, the PDQ-R is not suitable as a screening device in forensic populations. Semistructured interviews that make use of collateral information are recommended for diagnosing personality disorders in forensic subjects.

Adolescent↗

PubMed1998

Derivatization in capillary electrophoresis.

In recent years capillary electrophoresis (CE) has been developed into a versatile separation technique, next to gas and liquid chromatography (LC), well suited for the determination of a wide variety of e.g., pharmaceutical, biomedical and environmental samples. The main advantages of CE over chromatographic separation techniques are its simplicity and efficiency. It is well recognized, however, that the sensitivity and selectivity of the detection are relatively weak points of CE. One way to overcome these limitations is the conversion (derivatization) of the analytes into product(s) with more favourable detection characteristics. Although, in principle, almost any detection mode can be combined with a derivatization procedure, in practice, fluorescence monitoring is favoured in most cases. This paper aims to give a short overview on the various reagents that can be used for pre-, post- and on-column derivatization in CE. First, a short introduction is given on CE as an analytical technique, followed by a discussion of the pros and cons of the various modes of derivatization, a comparison of derivatizations in CE with derivatizations in LC, the principles of fluorescence and prerequisites for a good fluorophore and the potential of using diode lasers in combination with a labelling procedure. With respect to the derivatization reagents the emphasis is on the labelling of amino, aldehyde, keto, carboxyl, hydroxyl and sulfhydryl groups.

Amines↗

PubMed1997

Psychological functioning of adolescent transsexuals: personality and psychopathology.

Adolescent transsexuals were compared with adolescent psychiatric outpatients and first-year university students to determine the extent to which other psychopathology is a necessary condition for the development of transsexualism. Three areas of psychological functioning associated with fundamental psychological disturbances--perceptual inaccuracy, disorders of thought and negative self-image--were assessed by means of the Rorschach Comprehensive System. The group of adolescent transsexuals was found to be intermediate between adolescent psychiatric patients and nonpatients for extent of perceptual inaccuracy. They did not differ significantly from nonpatients with regard to thinking disturbances and negative self-image. The psychiatric patients included significantly more individuals characterized by negative self-image than the other groups. The results support the idea that major psychopathology is not required for the development of transsexualism.

Adaptation, Psychological↗

PubMed1997

Attachment representations of personality-disordered criminal offenders.

The relation between attachment representations and personality disorders was examined in a sample of 40 Dutch men held in a forensic psychiatric hospital for the commission of serious crimes. Secure attachment representations were virtually absent in the sample; separation from attachment figures in childhood was related to current insecure attachment as well as to personality disorders. Use of attachment theory in research and clinical work with criminals is discussed.

Adult↗

PubMed1994

The emotional Stroop interference effect in anxiety: attentional bias or cognitive avoidance?

Interference effects on threat words in anxious subjects on the emotional Stroop task have generally been interpreted as evidence for mood-congruent attentional bias in anxiety states. However, several recent studies have yielded results that run contrary to this attentional bias explanation. The most important of these conflicting findings show that: (1) panic disorder patients displayed interference on threat words, but also on other emotional words, including positively valenced words, and (2) 'repressors' showed even greater interference than high trait anxious subjects. We propose an alternative explanation for these findings, in which both attentional bias and cognitive avoidance are assumed to operate in the emotional Stroop task, but in which cognitive avoidance is hypothesized to be chiefly responsible for the greater interference effects found in anxious subjects and 'repressors'. We suggest that future research into cognitive processes associated with anxiety states should employ a variety of experimental paradigms on the same subjects and include measures of 'defensiveness'.

Anxiety↗

PubMed1994

Role of the donor liver in the origin of platelet disorders and hyperfibrinolysis in liver transplantation.

We investigated the role of the donor liver in the origin of platelet disorders and hemostatic defects in liver transplantation. Eighteen pigs received an orthotopic or a heterotopic, auxiliary liver graft. Liver biopsies were taken for electron microscopic studies 5-10 min after reperfusion in nine animals. Blood samples were taken from the first hepatic outflow and from the systemic circulation before and 5 min after graft recirculation. Electron microscopy did not show any evidence of microthrombi or platelet aggregation in the graft, either after orthotopic liver transplantation or after heterotopic liver transplantation. Most blood platelets, which were lying free in the sinusoids, showed cell processes and many seemed to have lost their granulae, suggesting a degree of platelet activation. There were also signs of phagocytosis of platelets by the Kupffer cells. In the hepatic outflow, platelet count was significantly lower (p < 0.05) and fibrinolytic activity significantly higher (p < 0.01), than systemic post-reperfusion values. There were no important changes in the coagulation parameters. No significant changes were found between the effects on hemostasis of orthotopic and auxiliary graft reperfusion. In the second part of the study evidence for platelet activation was found after graft reperfusion in human liver transplantation. Plasma levels of platelet factor-4 and beta-thromboglobulin increased significantly after graft reperfusion. These studies suggest that platelet disorders and increased fibrinolytic activity are the major components of the hemostatic defect after graft recirculation in liver transplantation. Sequestration of platelets in the graft is probably due to the accumulation of (activated and degranulated) platelets in the sinusoids and phagocytosis by Kupffer cells.

Animals↗

PubMed1992

The role of hyperventilation in panic disorder: a response to Ley (1991)

Ley (Behaviour Research and Therapy, 29, 301-304, 1991) provided a reinterpretation of experimental findings on the efficacy of breathing retraining plus cognitive restructuring in reducing the symptomatology of patients with panic disorder with agoraphobia which were presented in a 1989 article in this journal. On the basis of his reinterpretation, they concluded that our findings supported the central role of hyperventilation in panic attacks. Ley's arguments are discussed and we conclude that his reinterpretation provides new arguments against a hyperventilation theory of panic. Furthermore, recent evidence from empirical studies does not support a central role for hyperventilation in panic attacks.

Arousal↗

PubMed1992

A follow-up study on short-term treatment of agoraphobia.

The differential effectiveness of three treatment packages for agoraphobia was tested. Patients received one of three short-term treatments: Breathing Retraining and Cognitive Restructuring, graded Self-Exposure in vivo, or a combination of both. No differential effects were found between the treatment conditions at posttest and at an 18 months follow-up. Improvement at follow-up assessment was associated with whether patients had further treatment during the follow-up period. No relationship was found between further improvement and demographic variables, pre- and posttest scores on psychological questionnaires or the use of medication at follow-up. Implications of these findings are examined.

Adult↗

PubMed1992

Personality in panic disorder with agoraphobia: a Rorschach study.

In this study, we tested several hypotheses derived from self psychology (Diamond, 1987) regarding personality features of patients suffering from panic disorder and agoraphobia (PDA). PDA patients are thought to suffer from a deficit in negative affect-regulating capacity, surrounded by defenses such as avoidance, repression, denial, and reaction formation against dependency needs. These defenses are thought to lead to a greatly impoverished affective life. The Rorschach Comprehensive System was used to assess the personality features of avoidance, restricted affective life, and reaction formation against dependency needs. We found evidence for the presence of a highly avoidant information-processing style (86% of protocols had lambda [L] greater than .99) and a constricted affective life (low weighted sum color [WSumC] and low affective ratio [Afr]). Our results were consistent with the hypothesis of reaction formation against dependency needs (low food content [Fd]). Findings are discussed in light of studies that found a high incidence of avoidant personality disorder in PDA patients.

Adult↗

PubMed1990

Liquid chromatographic determination of pentachlorophenol in serum, using pre-column phase-transfer catalysed dansylation and post-column photolysis with fluorescence detection.

Dansylation of pentachlorophenol was carried out after solid-phase extraction of acidified human serum and desorption with dichloromethane, in a dichloromethane-water two-phase system using tetrabutyl-ammonium bromide as the phase-transfer catalyst. Derivatisation was complete within 2 min at room temperature. After evaporation of an aliquot of the organic phase, the residue was dissolved in methanol and injected into a reversed-phase chromatographic system, equipped with a post-column photochemical reactor. In the reactor, dansylated pentachlorophenol is converted into highly fluorescent products. The recovery of the analyte from serum was 85 +/- 4%. Calibration graphs for horse and human serum were linear over two decades, with correlation coefficients ranging from 0.996 to 0.999. The detection limit of pentachlorophenol in horse and human serum was 400 pg ml-1. The reproducibility of the total procedure for a human serum sample containing 4 ng ml-1 was 4.5%.

Catalysis↗

PubMed1989

The hyperventilation syndrome in panic disorder, agoraphobia and generalized anxiety disorder.

The symptom complex of panic disorder and generalized anxiety disorder suggests an etiological role for hyperventilation. The present study investigates the overlap between DSM-III-R panic disorder, panic disorder with agoraphobia and generalized anxiety disorder with hyperventilation syndrome (HVS). The anxiety disorder diagnoses were based on a structured interview, and HVS syndrome (HVS). The anxiety disorder diagnoses were based on a structured interview, and HVS determined by the so-called hyperventilation provocation test (a brief period of voluntary hyperventilation with recognition of symptoms). The overlap rates with HVS were: 48% for panic disorder, 83% for panic disorder with agoraphobia and 82% for generalized anxiety disorder. However, a pilot study on transcutaneous monitoring of carbon dioxide tension leads us to question the validity of the voluntary hyperventilation method that we used to determine HVS-status. It is unclear whether hyperventilation plays an important role in panic and general anxiety, as our overlap findings suggest. For patients who recognize the symptoms induced by voluntary hyperventilation, the hyperventilation provocation procedure provides a therapeutic means of exposure to feared bodily sensations.

Adult↗

PubMed1989

Breathing retraining, exposure and a combination of both, in the treatment of panic disorder with agoraphobia.

The present study investigates the differential effectiveness of three treatment packages for agoraphobia. Patients suffering from panic disorder with agoraphobia (DSM-III-R) received one of three treatments: Breathing Retraining with Cognitive Restructuring (BRCR), graded self-exposure in vivo (EXP), or a combination of BRCR and EXP. Treatments consisted of 8 sessions. Assessment consisted of self-report measures for panic, phobic anxiety and avoidance, depression, general anxiety, somatic complaints and fear of body sensations, and of two respiratory measures (respiratory rate and alveolar pCO2). The treatments resulted in a reduction in symptomatology on all self-report measures, except panic frequency, and in a decrease in respiratory rate. There was no evidence for a differential efficacy for any of the treatments on any of the variables. Contrary to expectation, and at odds with findings from earlier studies, BRCR had no significant effect on panic frequency. A detailed comparison of sample characteristics of patients in our study and previous studies, did not yield insight into possible causes for the failure to replicate earlier results. The limited effectiveness of breathing retraining in reducing panic, as observed in the present study, leads us to conclude that the role of hyperventilation in panic is less important than previously thought.

Adult↗

PubMed1989

Conditioning experiences and phobias.

A retrospective study was conducted to examine the extent to which phobias are associated with a conditioning pathway to fear. The Phobic Origin Questionnaire (Ost and Hugdahl, Behav. Res. Ther. 19, 439-477, 1981) was administered to a sample of 91 phobic outpatients (patients with panic disorder with agoraphobia, social phobics, simple phobics). Results show clearly that conditioning experiences occur more frequently than either vicarious or informational, learning experiences, which confirms the findings previously reported by Rimm, Janda, Lancaster, Nahl and Dittmar (Behav. Res. Ther. 15, 231-238, 1977) and by Ost and Hugdahl (1981; Behav. Res. Ther. 21, 623-631, 1983). Yet, conditioning experiences consist mainly of panic attacks in confirmed environments. The findings also suggest that a considerable number of phobias are based on a combination of different pathways to fear.

Adult↗

PubMed1989

Handedness and anxiety in normal and clinical populations.

Previous research has yielded inconclusive evidence as to the relationship between handedness and anxiety. In order to further examine this relationship, two studies were carried out. In the first study, university students (N = 167) completed the Edinburgh Handedness Inventory, the Fear Questionnaire, and the Maudsley Obsessive Compulsive Inventory. No evidence was found to suggest that phobic fears are more prevalent or more severe among individuals with a tendency to left-handedness than among pure right-handers. Statistical tests reveled a marginally significant positive association between social phobia scores and right-handedness. In the second study, handedness was assessed in 77 anxiety disorder patients and compared with handedness patterns in normal controls. Again, no support was found for the claim that anxiety and left-handedness are related to each other. However, the normal pattern of women being more right-handed than men was reversed in the anxiety disorder group.

Adult↗

PubMed1988

Effects of the ortho-quinone and catechol of the antitumor drug VP-16-213 on the biological activity of single-stranded and double-stranded phi X174 DNA.

We have studied the effects of the recently reported two new metabolites of the antitumor agent VP-16-213, the ortho-dihydroxy derivative or catechol and the ortho-quinone, on the biological activity of single-stranded and double-stranded phi X174 DNA, the binding of the metabolites to calf thymus DNA and the conversion of the catechol into the ortho-quinone. Evidence was obtained for the oxidation of the catechol into the ortho-quinone and for the fact that the ortho-quinone is the metabolite of VP-16-213 responsible for its binding to rat liver microsomal proteins. The catechol and ortho-quinone of VP-16-213 were found to bind 7-9 times more strongly to calf thymus DNA than VP-16-213 itself. In contrast to the parent compound VP-16-213, the catechol as well as the ortho-quinone inactivated both single-stranded (ss) and double-stranded (RF) biologically active phi X174 DNA. The mean T37-values for inactivation of ss and RF phi X174 DNA by 2.2 x 10(-4)M catechol at 37 degrees and pH 7.4 were 96 and 640 min, respectively. Reduction of the ortho-quinone by NADPH cytochrome P-450 reductase resulted in formation of the catechol. The system ortho-quinone/NADPH cytochrome P-450 reductase inactivated ss phi X174 DNA with a mean T37-value of 454 min, and this inactivation was inhibited by DMSO. The mean T37-value for inactivation of ss phi X174 DNA by 1.8 x 10(-4) M ortho-quinone at 37 degrees and pH 4.0 was 24 min. The chemical stability of the ortho-quinone and the extent of inactivation of ss phi X174 DNA by the ortho-quinone were both pH-dependent: at higher pH the ortho-quinone was less stable and gave less inactivation of DNA. The aqueous decomposition product(s) of the ortho-quinone formed at pH 7.4 inactivated ss phi X174 DNA with a mean T37-value of 175 min. The rate of inactivation of RF phi X174 DNA by the ortho-quinone at pH 4.0 was twice as low as the rate of inactivation of ss phi X174 DNA: T37 = 49 min. When using excision repair deficient E. coli mutants (uvrA- or uvrC-), a higher inactivation of RF phi X174 DNA was found: T37 = 29 min for uvrA- E. coli, indicating that a part of the DNA damage introduced by the incubation with ortho-quinone is removed by excision repair.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1985

Inactivation of phi X174 DNA by the ortho-quinone derivative or its reduction product of the antitumor agent VP 16-213.

Biologically active phi X174 DNA is inactivated by the ortho-quinone derivative of the antitumor agent VP 16-213, but not by VP 16-213 itself, VP 16-213 phenoxy radical or aqueous decomposition product(s) of the ortho-quinone. Reduction of the ortho-quinone by cytochrome P-450 reductase and NADPH results in deactivation of the ortho-quinone towards anti-phi X174 DNA activity. However, compared with the parent compound VP 16-213, reduction of the ortho-quinone results in substantial damage towards DNA.

Bacteriophage phi X 174↗

PubMed1985

The role of metabolic activation by cytochrome P-450 in covalent binding of VP 16-213 to rat liver and HeLa cell microsomal proteins.

Covalent binding of 3H-labeled VP 16-213 to rat liver and HeLa cell microsomal proteins was studied in vitro. Metabolic activation by cytochrome P-450 was found to play a role in the covalent binding of VP 16-213 to rat liver microsomal proteins, as shown by the need of NADPH cofactor, the increased binding after phenobarbital pretreatment and the inhibition by SFK-525A. Addition of ascorbic acid or alpha-phenyl-N-tert. butylnitrone to the incubation mixture depressed covalent binding by about 85%, suggesting that formation of a reactive metabolite from the phenolic structure may be involved in the binding process. VP 16-213 did not inhibit aminopyrine N-demethylase at the concentration used in the binding experiments (17 microM), indicating that metabolism of its methylenedioxy group does not play a role in binding to microsomal proteins. HeLa cell microsomes were found to possess aminopyrine N-demethylase activity. Covalent binding of radiolabeled VP 16-213 to HeLa cell microsomes decreased by about 64% if NADPH was omitted.

Animals↗

PubMed1983

Automated liquid chromatographic analysis of the anti-tumorigenic drugs etoposide (VP 16-213) and teniposide (VM 26).

A method is described for the fully automated analysis of large numbers of 1--2 ml serum and plasma or urine samples containing the anti-tumorigenic drugs etoposide and teniposide and their aglycone. The blood samples are hydrolysed by a proteolytic enzyme, subtilisin A, prior to preconcentration on a small precolumn. The hydrolysis step serves both to release the strongly protein-bound drugs and to prevent clogging of the chromatographic system. On-line preconcentration is carried out with precolumns packed with PRP1, a micro-particulate divinylbenzene-styrene copolymeric sorbent. Chromatography takes place, after column switching, in a C18/methanol--water system. After a post-column clean-up step using continuous extraction with dichloroethane in an autoanalyzer system, native fluorescence of these analytes is used for detection of the drugs. Recovery of etoposide and teniposide from spiked serum and plasma samples was 100%. Calibration curves of etoposide and teniposide typically show correlation coefficients of 0.9994 over a two-to-three order linear range. The detection limit of etoposide is approx. 8 ng per sample. Repeatability was found to be excellent. Unattended overnight routine analysis is possible without any problems. This method, considering optimal sample throughput, reliability and selectivity, competes favourably with existing techniques for the analysis of etoposide and teniposide.

Autoanalysis↗