Improvements of complex post-traumatic stress disorder symptoms during a multimodal psychodynamic inpatient rehabilitation treatment - results of an observational single-centre pilot study

Background: Complex post-traumatic stress disorder (CPTSD) describes chronic disturbances in self-organization (i.e. affect dysregulation; negative self-concept; severe difficulties in relationships) which are frequently observed in survivors of prolonged, repeated or multiple traumatic stressors. So far, evidence of psychodynamic treatment approaches for CPTSD is scarce.Methods: In this single-centre observational pilot study, symptom change during a 6-week psychodynamic inpatient treatment in a multimodal psychosomatic rehabilitation centre was evaluated using repeated measures analyses of variance (ANOVAs). Patients completed questionnaires on PTSD and CPTSD symptoms (ITQ), anxiety, depression and somatization (BSI-18), functional impairment (WHODAS) and epistemic trust, mistrust and credulity (ETMCQ) before (T1) and at the end of treatment (T2). A hierarchical linear regression analysis was calculated to identify factors associated with improved CPTSD symptoms.Results: A total of n = 50 patients with CPTSD were included in the study, of whom n = 40 (80%) completed treatment. Patients reported a significant reduction of CPTSD symptoms during treatment with a large effect size (-3.9 points; p < .001; η2 = .36), as well as a significant reduction of psychological distress (p < .001; η2 = .55) and functional impairment (p < .001; η2 = .59). At the end of treatment, 41.0% of patients no longer fulfilled the diagnostic criteria for CPTSD. Changes in epistemic stance included improved epistemic trust (β = -.34, p = .026) and decreased epistemic credulity (β = .37, p = .017), which together with lower age (β = .43, p = .012) and lower depression levels at baseline (β = .35, p = .054) were significantly associated with baseline adjusted mean change of CPTSD symptoms during therapy and explained 48% of its variance.Discussion: In our study, patients reported a significant reduction of CPTSD symptoms and comorbid symptoms during a multimodal psychodynamic inpatient rehabilitation treatment. Improved epistemic trust may facilitate the establishment of a trusting therapeutic relationship, thus fostering an environment of openness for knowledge transfer (i.e. social learning) and the exploration of diverse viewpoints and perspectives in the therapeutic process.

Using a quality of life (QoL)-monitor: preliminary results of a randomized trial in Dutch patients with early breast cancer

Purpose

The diagnosis and treatment of cancer negatively affect patients’ physical, functional and psychological wellbeing. Patients’ needs for care cannot be addressed unless they are recognized by healthcare providers (HCPs). The use of quality of life (QoL) assessments with feedback to HCPs might facilitate the identification and discussion of QoL-topics.

Methods

113 patients with stage I–IIIB breast cancer treated with chemotherapy were included in this randomized controlled trial. Patients were randomly allocated to receive either usual care, or usual care with an intervention consisting of a QoL-monitor assessing QoL, distress and care needs before every chemotherapy cycle visit. Patients completed questionnaires regarding QoL, illness perceptions, self-efficacy, and satisfaction with communication. From the 2nd visit onwards, patients in the intervention arm and their HCPs received a copy of the QoL overview and results were shown in patients’ medical files. Audio-recordings and patients’ self-reports were used to investigate effects on communication, patient management and patient-wellbeing. A composite score for communication was calculated by summing the number of QoL-topics discussed during each consultation.

Results

Use of the QoL-monitor resulted in a higher communication score (0.7 topics increase per visit, p = 0.04), especially regarding the disease-specific and psychosocial issues (p < 0.01). There were no differences in patient management, QoL, illness perceptions or distress. Patients in the experimental arm (n = 60) had higher scores on satisfaction with communication (p < 0.05).

Conclusions

Use of a QoL-monitor during chemotherapy in patients with early breast cancer might result in a more frequent discussion of QoL-topics, associated with high levels of patients’ satisfaction.

Electronic supplementary material

The online version of this article (10.1007/s11136-020-02549-8) contains supplementary material, which is available to authorized users.

Black TiO2 nanotubes: Efficient electrodes for triggering electric field-induced stimulation of stem cell growth

TiO₂ nanostructures represent a key platform for biomedical applications, due to the combination of biocompatibility and high surface area. Especially TiO₂ nanotube layers have been widely investigated due to controllable nanotopographic effects as well as for electrodes in electrostimulation experiments. In the present work we produce Ar/H₂-reduced 'black' TiO₂ nanotube arrays with a strongly enhanced electrical conductivity and explore their interaction with mesenchymal stem cells when used as electrodes to apply electric fields (EF) across the cells. While we observe no significant change in cell adhesion and their focal contact formation on these high conductivity nanotubes, we do observe a rapid stem cell response when EF is engaged using the 'black' TiO₂ nanotube arrays as electrodes. Compared to as-formed nanotube arrays, a faster stem cell growth was observed and a lower EF intensity caused an intracellular calcium level elevation. Our results indicate that the increased conductivity in TiO₂ nanotubes significantly enhances the early stem cell response to minimal electric field stimuli. STATEMENT OF SIGNIFICANCE: The use of TiO₂ nanostructures in biomedical applications is widely investigated, especially considering the nanostructured surface influence on the biomaterial-cell interactions. We have previously shown that an applied electric field (EF) on stem cells grown on TiO₂ nanotubes leads to synergistic osteogenic stimulation in the absence of biochemical bone-inducing supplements. Here we report that black (i.e. highly conductive nanotubes obtained by reduction treatments) TiO₂ nanotubes enable short-time EF effects on stem cells: we observe a faster stem cell growth and a significantly enhanced early stem cell response to minimal EF stimuli. The application of such nanostructures under electric field is promising for therapeutic interventions for bone regeneration and tissue engineering approaches.

Participation and mental well-being of mothers of home-living patients with spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) causes severe physical limitations but also has a major impact on the lives of parents. The aim of this study was to investigate participation and mental well-being (burden, emotional distress and satisfaction with participation) of parents of home-living patients with SMA. Caregiver burden was assessed with the Caregiver Strain Index, emotional distress with the Hospital Anxiety and Depression Scale and satisfaction with participation with the Utrecht Scale for Evaluation of Rehabilitation-Participation. Because the majority of parents were mothers of home-living SMA patients (76%), further analyses were restricted to mothers. Seventy-seven percent of mothers of patients with SMA had paid work. A substantial proportion of mothers (76%) perceived high caregiver burden. Burden, emotional distress and satisfaction with participation were comparable between mothers of children and mothers of adults with SMA. Caregivers' participation in leisure activities was significantly related to their perceived level of caregiver burden, emotional distress and satisfaction with participation. Mothers engaging in more social and leisure activities reported lower emotional distress and caregiver burden. Considering the high level of burden attention should be paid to mental well-being of primary caregivers of patients with SMA. Caregivers should be motivated to keep participating in social/leisure activities.

Cross-cultural comparison of breast cancer patients' Quality of Life in the Netherlands and Japan

Purpose

Cultural differences are hypothesized to influence patients’ Quality of Life (QoL) reports. However, there is a lack of empirical cross-cultural studies comparing QoL of patients with cancer. This study aims to compare QoL of women with breast cancer in the Netherlands and Japan, and to investigate the association of QoL with sociodemographic, clinical, and psychological variables (illness perceptions).

Methods

Dutch (n = 116) and Japanese (n = 148) women with early breast cancer undergoing chemotherapy completed the EORTC QLQ-C30 and Brief Illness Perception Questionnaire immediately before their second cycle of chemotherapy.

Results

Dutch women reported poorer Physical, Role, Emotional, and Cognitive functioning than Japanese women. Additionally, illness perceptions were significantly different in Japan and the Netherlands, but these did not vary across treatment type. In Japan, QoL of women receiving AC-chemotherapy was better than that of women receiving FEC-chemotherapy, whereas in the Netherlands, QoL did not vary as a function of chemotherapy. Illness perceptions about symptom severity, adverse consequences, and emotional representations were negatively related to most domains of patients’ QoL in both countries. Adding illness perceptions as covariates to the ANOVA analyses rendered the effects of country and treatment type on QoL non-significant.

Conclusions

Comparing Dutch and Japanese women with early breast cancer revealed important differences in treatment modalities and illness perceptions which both appear to influence QoL. Perceptions about cancer have been found to vary across cultures, and our study suggests that these perceptions should be considered when performing cross-cultural studies focusing on patient-reported outcomes.

Abstract OT3-1-03: DIRECT: A phase II/III randomized trial with dietary restriction as an adjunct to neoadjuvant chemotherapy for HER2-negative breast cancer

Background:

Preclinical evidence shows that short-term fasting protects normal cells, while cancer cells are sensitized to chemotherapy. Furthermore, a specifically designed very low calorie, low amino acid substitution diet (“Fasting Mimicking Diet”, FMD) has similar effects on chemotherapy as short-term fasting. This trial evaluates the impact of FMD on tolerance to and efficacy of neoadjuvant chemotherapy in women with HER2-negative early breast cancer.

Trial design:

DIRECT is a Dutch, randomized, open-label multicenter phase II/III trial. Women receiving neoadjuvant TAC courses (docetaxel/adriamycin/cyclophosphamide; day 1, q 3 weeks with G-CSF support at day 2) will be randomized with or without FMD for 3 days prior to and the day of chemotherapy and 3 days prior to surgery.

Eligibility criteria:

Eligible women are WHO 0-2, age ≥18 years, HER2-negative, stage II or III breast cancer and adequate bone marrow, liver and renal function, BMI &gt; 19kg/m2 and absence of diabetes mellitus.

Study endpoints:

The primary endpoints are grade III/IV toxicity (phase II) and the pathologic complete response rate (pCR) (phase III). Secondary endpoints are grade I/II toxicity, metabolic and inflammatory response to chemotherapy, DNA damage, apoptosis, immunology and nutrient sensing pathways in the tumor, biomarkers as single nucleotide polymorphisms, Ki67 and tumor stroma/ratio, patient's quality of life and (disease free) survival. Optional side studies include chemotherapy-induced DNA damage and nutrient sensing pathways in leukocytes and proteomics.

Statistical Methods:

Using a 5% significance level based on the two-sided Fisher's exact test with a power of 80%, 128 patients (64/arm) will be enrolled to show a 50% decrease of grade III/IV adverse events in the experimental arm (phase II) and 250 patients (125/arm) are needed to show an improvement of the pCR rate from 18% to 36% (phase III).

Target accrual:

Recruitment will start in September 2013. The expected end of accrual of 250 patients from multiple centers in the Netherlands will be the last quarter of 2015.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-1-03.

Demonstration of ignition radiation temperatures in indirect-drive inertial confinement fusion hohlraums

We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of T(RAD)=300 eV and a symmetric implosion to a 100 μm diameter hot core.

Participation and drop-out in pulmonary rehabilitation: a qualitative analysis of the patient's perspective

OBJECTIVE

To examine patients' pretreatment beliefs and goals regarding pulmonary rehabilitation.

DESIGN

Qualitative study using semi-structured interviews.

SETTING

Interviews conducted at participants' homes.

SUBJECTS

Twelve patients with chronic obstructive pulmonary disease who had been referred to a rehabilitation clinic.

MAIN MEASURES

Patients' beliefs about pulmonary rehabilitation, self-set treatment goals and anticipated reasons for drop-out.

RESULTS

Patients' beliefs about pulmonary rehabilitation comprised positive aspects (participation as an opportunity for improvement, a safe and multidisciplinary setting, presence of motivating and supporting patients) and negative aspects of exercising in a rehabilitation centre (e.g. disruption of normal routine, being tired after training, transportation difficulties, limited privacy and confrontation with severely ill patients). Four types of treatment goals were formulated: increase in functional performance, weight regulation, reduction of dyspnoea, and improvement of psychosocial well being. Four clusters of anticipated reasons for drop-out were identified: the intensity of the programme, barriers to attending (e.g. transportation problems, sudden illness and other duties/responsibilities), lack of improvement and social factors. Four different attitudes towards pulmonary rehabilitation could be distinguished: optimistic, 'wait and see', sceptic and pessimistic. Follow-up data revealed that whereas a pessimistic attitude (high disability, low self-confidence, many concerns) was related to decline, the 'sceptic' patients had dropped out during the course.

CONCLUSIONS

Uptake and drop-out may be related to patients' perceived disabilities, expected benefits and concerns with regard to rehabilitation, practical barriers and confidence in their own capabilities.

Symptomatic reversible duodenal compression due to iatrogenic retroperitoneal hematoma

Selective serotonin reuptake inhibitors are frequently employed to treat depression. However, although rarely, coagulation abnormalities have been described following the use of these compounds, and these effects appear to be enhanced by simultaneous use of nonsteroidal anti-inflammatory drugs. We describe a case of reversible symptomatic duodenal compression caused by a retroperitoneal hematoma after ingestion of sertraline and nimesulide.

Exploring computational lead optimisation with affinity constants obtained by surface plasmon resonance for the interaction of PorA epitope peptides with antibody against Neisseria meningitidis

LUDI is a program used for de novo structure-based design of ligands and can predict binding of ligands quantitatively using a scoring function. Here we evaluate LUDI in a lead optimisation study with ligands for the antibody MN12H2, that has been raised against outer membrane protein PorA epitope P1.16 of Neisseria meningitidis. The ligands were synthetic peptides that are derived from the smallest binding epitope (182)DTNNN(186). LUDI's fragment building rules are used for the proposal of new peptide-ligands for MN12H2 and were focused on replacements of Asp(186) in the epitope. Accordingly, a series of peptides was synthesised with isosteric mutations. The interaction of the peptides with MN12H2 was analysed with a surface plasmon resonance competition assay yielding equilibrium binding constants in solution (K(S)). The binding affinity seems to be largely determined by entropy, and the side chain of Asn(186) is sensitive for charge, inversion, hydrophobicity and size. Head-to-tail cyclisation of the peptide in a nine-amino-acid ring gives little reduction in affinity. It is concluded that the scoring function of LUDI does not help in optimisation of the peptide lead for MN12H2 binding. Other more elaborate molecular mechanics calculations show similar results. This implies that our current knowledge of molecular recognition is insufficient for explaining a case of peptide-protein binding, where the design process requires subtle changes in structure (from lead finding to lead optimisation).

Bcl-2 mediates sex-specific differences in recovery of mice from LPS-induced signs of sickness independent of IL-6

Chronic pulmonary diseases are more common in boys than in girls. Therefore, we investigated the differences in signs of sickness in male and female mice that were exposed to lipopolysaccharide (LPS) by intranasal instillation. Because apoptosis is important in the resolution of inflammation, we tested the hypothesis that reduced levels of Bcl-2, a regulator of apoptosis, may play a role in gender-specific differences in response to inflammation. Bcl-2 wild-type (+/+) female mice recovered from an LPS-induced drop in body temperature and loss in body weight significantly faster than male (+/+) mice. Female heterozygous (+/-) mice showed reduced Bcl-2 levels and exhibited a slower recovery than female (+/+) mice that was similar to the recovery pattern in male (+/+) and (+/-) mice. Interleukin-6 (IL-6) activity levels in the bronchoalveolar lavage fluid were higher in male than in female mice but were not different between (+/+) and (+/-) mice. We conclude that Bcl-2 plays a role in mediating the faster recovery of female (+/+) mice from LPS-induced signs of sickness independent of IL-6. These studies indicate that apoptotic mechanisms may be involved in gender-specific differences in chronic pulmonary diseases.

Excitatory nicotinic and desensitizing muscarinic (M2) effects on C-nociceptors in isolated rat skin

The actions of different cholinergic agonists and antagonists were investigated on nociceptive afferents using the rat skin-saphenous nerve preparation, in vitro. Nicotine was able to weakly excite C-nociceptors and to induce a mild sensitization to heat stimulation (in 77% of tested fibers) in a dose-dependent manner (10(-)6 to 10(-)5 m), but it caused no alteration in mechanical responsiveness tested with von Frey hairs. Muscarine did not induce a significant nociceptor excitation, but almost all fibers exhibited a marked desensitization to mechanical and heat stimuli in a dose-dependent manner (from 10(-)6 to 10(-)4 m). The muscarinic effects could be prevented by the general muscarinic antagonist scopolamine (10(-)5 m), by the M3 antagonist 1,1-dimethyl-4-diphenylacetoxypiperidium oxide (10(-)6 m) co-applied with the M2 antagonist gallamine (10(-)5 m), and by gallamine alone. As positive control we used the relatively M2-selective agonist arecaidine (10(-)6 to 10(-)5 m), obtaining a similar desensitizing effect as with muscarine. Finally, we performed an immunocytochemical study that demonstrated the presence of M2 but not M3 receptors in thin epidermal nerve fibers of the rat hairy skin. Altogether, these data demonstrate opposite effects of nicotinic and muscarinic receptor stimulation on cutaneous nociceptors. M2 receptor-mediated depression of nociceptive responsiveness may convey a therapeutic, i.e., analgesic or antinociceptive, potential.

Peptoid - peptide hybrids that bind Syk SH2 domains involved in signal transduction

Peptoid-peptide hybrids are oligomeric peptidomimetics that contain one or more N-substituted glycine residues. In these hybrids, the side chains of one or several amino acids are "shifted" from the alpha-carbon atom to the amide nitrogen atom. A library of phosphorylated peptoid-peptide hybrids derived from the sequence pTyr-Glu-Thr-Leu was synthesized and tested for binding to the tandem SH2 domain of the protein tyrosine kinase Syk. A considerable influence of the side chain position was observed. Compounds 19-21, 24, and 25 comprising a peptoid NpTyr and/or NGlu residue did not show any binding. Compounds 22, 23, and 26 containing an NhThr (hThr=homothreonine) and/or NLeu peptoid residue showed binding with IC(50) values that were only five to eight times higher than that of the tetrapeptide lead compound 18. These data show that side chain shifting is possible with retention of binding capacity, but only at the two C-terminal residues of the tetramer. This method of a peptoid scan using peptoid-peptide hybrids appears to be very useful to explore to what extent a peptide sequence can be transformed into a peptoid while retaining its affinity.

Bcl-2 in LPS- and allergen-induced hyperplastic mucous cells in airway epithelia of Brown Norway rats

Environmental toxins, infection, and allergens lead to a transient mucous cell hyperplasia (MCH) in airway epithelia; however, the mechanisms for reducing mucous cell numbers during recovery are largely unknown. This study investigated Bcl-2 expression in mucous cells induced by a neutrophilic or eosinophilic inflammatory response. Brown Norway rats intratracheally instilled with lipopolysaccharide (LPS) showed an inflammatory response characterized primarily by neutrophils. Secreted mucin was increased fourfold at 1 day, and the number of mucous cells was increased fivefold 2, 3, and 4 days post-LPS instillation compared with those in noninstilled rats. None of the mucous cells in non- or saline-instilled control animals expressed Bcl-2, whereas 20-30% of mucous cells were Bcl-2 positive 1 and 2 days post-LPS instillation. Brown Norway rats immunized and challenged with ovalbumin (OVA) for 2, 4, and 6 days showed an inflammatory response characterized primarily by eosinophils. Secreted mucin increased fivefold, and mucous cell number increased fivefold after 4 and 6 days of OVA exposure compared with water-immunized control rats challenged with OVA aerosols. Approximately 10-25% of mucous cells were Bcl-2 positive in OVA-immunized and -challenged rats. These data demonstrate Bcl-2 expression in hyperplastic mucous cells of Brown Norway rats regardless of the type of inflammatory response and indicate that apoptotic mechanisms may be involved in the resolution of MCHs.

Kinetic analysis of the mass transport limited interaction between the tyrosine kinase lck SH2 domain and a phosphorylated peptide studied by a new cuvette-based surface plasmon resonance instrument

We explored the use of a newly developed cuvette-based surface plasmon resonance (SPR) instrument (IBIS) to study peptide-protein interactions. We studied the interaction between the SH2 domain of lck and a phosphotyrosine peptide EPQY*EEIPIYL which was immobilized on a sensor chip. No indications for mass transport limitation (MTL) were observed when standard kinetic approaches were used. However, addition of competing peptide during dissociation revealed a high extent of rebinding. A dissociation rate constant (k(d)) of 0.6+/-0.1 s(-1) was obtained in the presence of large amounts of peptide. A simple bimolecular binding model, applying second-order kinetics for the cuvette system, could not adequately describe the data. Fits were improved upon including a step in the model which describes diffusion of the SH2 domain from the bulk to the sensor, especially for a surface with high binding capacity. From experiments in glycerol-containing buffers, it appeared that the diffusion rate decreased with higher viscosity. It is demonstrated that MTL during association and dissociation can be described by the same diffusion rate. A binding constant (K(D)) of 5.9+/-0.8 nM was obtained from the SPR equilibrium signals by fitting to a Langmuir binding isotherm, with correction for loss of free analyte due to binding. An association rate constant k(a) of 1.1(+/-0.2)x10(8) M(-1) x s(-1) was obtained from k(d)/K(D). The values for k(a) and k(d) obtained in this way were 2-3 orders larger than that from standard kinetic analysis, ignoring MTL. We conclude that in a cuvette the extent of MTL is comparable to that in a flow system.

Mechanism of action of the nonlipophilic antiallergic drug eclazolast (REV 2871) in the inhibition of mediator release in a mast cell model

OBJECTIVE AND DESIGN

In this study, we compared eclazolast with other lipophilic antiallergic drugs, relating to effects on signal transduction pathways, leading to inhibition of exocytosis in a rat basophilic leukemia cell (RBL-2H3).

MATERIALS AND METHODS

Effects of the drugs on mediator release (beta-hexosaminidase, arachidonic acid metabolites) after Fc(epsilon)RI activation in RBL-2H3 cell were quantified. Furthermore, effects of the drugs on cellular signalling (Ca2+ influx, intracellular Ca2+ concentration, inositol 1,4,5-trisphosphate (IP3) concentration) were assayed. Effects of the drugs on bilayer and cell membranes have been recorded.

RESULTS

It is shown that eclazolast down-regulates IP3 levels. In contrast to lipophilic drugs, eclazolast does not affect artificial bilayers and erythrocyte membranes, and there is no effect on thapsigargin induced Ca2+ influx. The effect of eclazolast was highly dependent on the antigen concentration with which the cells were triggered.

CONCLUSIONS

The mechanism of action of eclazolast is deviant from lipophilic antiallergic agents. It inhibits exocytosis by intracellularly affecting only direct Fc(epsilon)RI linked processes and not through inhibition of Ca2+ influx channels, as found for membrane disturbing lipophilic drugs.

Influence of the antiallergic drug oxatomide and derivatives on membrane structures: relation with inhibition of calcium influx in rat basophilic leukemia cells

Oxatomide is an H1 antihistaminic drug that also inhibits mediator release from mast cells. From previous studies, it appeared that inhibition of the influx of extracellular calcium is the major cause of this inhibition of exocytosis. Here, we explored the role of drug-membrane interactions in the inhibition of mediator release. We investigated the effects on phase transition and fluidity of artificial membranes. All compounds studied distorted the phase transition in L-alpha-dipalmitoylphosphatidylcholine liposomes, which correlated with the drug-induced increase in membrane fluidity measured by fluorescence anisotropy of the bilayer interacting probe 1-[4-(trimethylamino)-phenyl]-6-phenylhexa-1,3,5-triene. Erythrocytes were used to study membrane effects on a cellular level. The hypotonic-induced haemolysis of erythrocytes was inhibited by the drugs. Compounds which increased membrane fluidity of liposomes to a greater extent were also more active in decreasing haemolysis. Drug-induced disturbance of the membranes is related to their effect on the activity of store-operated Ca2+ channels. The activity of these channels in rat basophilic leukemia cells, assayed as 45Ca2+ influx, was most effectively inhibited by oxatomide derivatives, thereby inducing a more rigid membrane structure. Small changes in molecular structure affect the activity of the drugs and these structure-activity relations are discussed.

Effects of oxatomide and derivatives on high affinity IgE receptor-activated signal transduction pathways in rat basophilic leukemia cells: role of protein tyrosine hyperphosphorylation and inhibition of extracellular calcium influx

The antiallergic drug oxatomide and analogs inhibit mediator release from a rat basophilic leukemia (RBL-2H3) cell line, which is frequently used as a mast cell model. By investigating a series of derivatives of oxatomide with different inhibiting activities on exocytosis, we aimed to evaluate the role of their effects on the early steps of the signal transduction cascade in the inhibition of exocytosis. The active compounds induced hyperphosphorylation of tyrosine residues both in stimulated as well as in resting cells. Furthermore, some elevation of the inositol 1,4,5-trisphosphate (IP3) formation upon antigen activation was observed for the active derivatives. Ca2+ fluxes were also studied. The inhibition of the antigen-induced 45Ca2+ influx correlated with the effects of the drugs on exocytosis. Furthermore, the inhibitory activity on antigen- and thapsigargin-mediated exocytosis correlated well. Adherence of the cells to fibronectin, stimulating cellular integrin receptors, was synergistic to antigen activation of the RBL cells. However, oxatomide did lack any effect on integrin-mediated processes, as the IC50 value for exocytosis was identical for fibronectin-adhered cells and standard cultured cells. We conclude that oxatomide and its analogs inhibit exocytosis, mainly by inhibiting Ca2+ influx over store-operated Ca2+ (SOC) channels. The drugs have a direct effect on the store-operated Ca2+ channels or affect the direct regulation of these channels.

Structure-activity relationships of astemizole derivatives for inhibition of store operated Ca2+ channels and exocytosis

The effects of a series of analogues of the antiallergic drug astemizole on the exocytosis of the enzyme beta-hexosaminidase were studied in a mast cell model, the rat basophilic leukemia (RBL-2H3) cell. Besides differences in the effects on Fc epsilonRI receptor-stimulated exocytosis, changes were also observed in Ca2+ influx and in the perturbation of the cell membrane. A strong correlation was found between the effects on antigen- and thapsigargin-stimulated 45Ca2+ influx. Furthermore, the inhibition of 45Ca2+ influx was correlated with the inhibition of beta-hexosaminidase release and membrane stabilization. It is concluded that the astemizole analogues are capable of inhibiting mast cell beta-hexosaminidase release through inhibition of Ca2+-store-operated Ca2+ channels (SOC). Compounds with high lipophilicity also released Ca2+ from intracellular stores. Lowering of the hydrophobicity by introduction of nitrogens or truncation at different sites in the astemizole structure decreased inhibitory activity on SOC channels. The inhibition of SOC channels cannot completely be ascribed to non-specific membrane effects. The piperidinyl-benzimidazole moiety was found to be important for inhibition of SOC channels. The observed differences in activity possibly depend on the way the compounds penetrate the membrane bilayer. Astemizole is an interesting new tool to study SOC channels and can be a lead for the design of mast cell-stabilizing antiallergic drugs.

Dual effect of the anti-allergic astemizole on Ca2+ fluxes in rat basophilic leukemia (RBL-2H3) cells: release of Ca2+ from intracellular stores and inhibition of Ca2+ release-activated Ca2+ influx

The antiallergic drugs astemizole and norastemizole inhibit exocytosis in mast cells, which might be relevant for their therapeutic action. From previous studies, it appeared that the drugs inhibited 45Ca2+ influx. Here, we present a more detailed study on the effects of astemizole and norastemizole on Ca2+ fluxes. Fura-2-loaded rat basophilic leukemia (RBL-2H3) cells were activated through the high-affinity receptor for IgE (FcepsilonRI) with antigen or by the endoplasmatic reticulum ATPase inhibitor thapsigargin, bypassing direct FcepsilonRI-related events. It appeared that astemizole (>15 microM), in contrast to norastemizole, showed a dual effect on intracellular calcium concentration ([Ca2+]i): a rise in intracellular calcium concentration was induced, which originated in the release of intracellular Ca2+ stores, whereas Ca2+ influx via store-operated Ca2+ (SOC) channels was inhibited. Ca2+ influx was further characterized using Ba2+ influx, whereas processes in the absence of Ca2+ influx were studied using Ni2+ or EGTA. It was concluded that the drugs most likely affect the store-operated Ca2+ channels in RBL cells directly. The two effects of astemizole on Ca2+ fluxes had opposing influences on exocytosis, thereby accounting for the biphasic effect of increasing astemizole concentration on mediator release in RBL cells.

Effects of the anti-allergics astemizole and norastemizole on Fc epsilon RI receptor-mediated signal transduction processes

The non-sedating anti-allergic drug astemizole, apart from its potential to antagonise H1 receptors, inhibits the release of inflammation mediators from mast cells. To study the mechanism of this inhibition, we investigated the effects of astemizole and one of its active metabolites, norastemizole, on different phases of Fc epsilon RI (the high affinity receptor for the immunoglobulin IgE) receptor-activated signal transduction in rat basophilic leukemia cells (RBL-2H3), leading to exocytosis. Cells were stimulated either through antigen, or thapsigargin, or synergistic combinations of Fc epsilon RI receptor activation with either adenosine A3 receptors or integrins, activated by fibronectin adherence. The effects of the drugs on mediator release, inositol 1,4,5-trisphosphate formation, tyrosine phosphorylation of cellular proteins and Ca2+ fluxes were investigated. Inositol 1,4,5-trisphosphate levels are not affected. Astemizole increased tyrosine phosphorylation in resting cells, especially a 96-kDa protein band. Particularly tyrosine phosphorylation related to post Ca2+ processes is changed after cell triggering in the presence of astemizole. Both drugs inhibit the influx of 45Ca2+, with similar dose response curves as for the inhibition of exocytosis. Astemizole but not norastemizole, when used in resting cells, released Ca2+ from intracellular stores. Astemizole (> 15 microM) also induced exocytosis in resting cells. It did not induce additional changes in its inhibiting effect when cells were triggered with synergistic combinations of Fc epsilon RI receptor activation with either adenosine A3 receptors or integrins. Effects on haemolysis of erythrocytes and differential scanning calorimetry in liposomes showed clear differences in membrane perturbation between astemizole and norastemizole. The observed differences, and the role of membrane perturbation in the action on Ca2+ fluxes, are discussed.

Relation between effects of a set of anti-allergic drugs on calcium pathways and membrane structure in Fc epsilon RI activated signal transduction

The antigen induced stimulation of mast cells by aggregation of Fc epsilon RI receptors activates a signal transduction cascade leading to release of mediators of inflammation like histamine, arachidonic acid metabolites and cytokines. In this study we investigated a series of structurally related anti-allergic drugs, containing a common lipophilic diphenylmethyl piperazinyl tail and head groups that differ in lipophilicity. Effects of these drugs on various steps of the signal transduction cascade was investigated to gain insight into the mechanism of action of these drugs. It appeared that addition of the drugs to resting cells induced changes in the tyrosine phosphorylation of cellular proteins. The most active anti-allergics in inhibiting exocytosis, AL3264 and oxatomide, also induced the largest changes in phosphorylation. The effects of the drugs on tyrosine phosphorylation after cell activation was complex. Additionally, Ca2+ fluxes were investigated. Ca2+ efflux from the cells was negligibly influenced by the active drugs. However, the drugs inhibited influx from extracellular Ca2+, which was correlated with the effects of the drugs on inhibition of exocytosis and on membrane stabilization induced by the drugs, measured as haemolysis of erythrocytes. It is concluded that inhibition of Ca2+ influx is the major mechanism with which these drugs inhibit exocytosis and that for this effect drug-membrane interactions, possibly affecting the function of membrane embedded proteins, are of importance. Possible mechanisms including drug-membrane interactions, phosphorylation and inhibition of Ca2+ influx are discussed.

Influence of the anti-allergic drug oxatomide on the signal transduction mechanism in a mast cell model

In a mast cell model, oxatomide displays inhibition of mediator release which is not related to its histamine H1 receptor antagonistic activity. From a previous study it appeared that especially early steps in the signal transduction leading to exocytosis were influenced by oxatomide. We now studied effects of oxatomide on those early steps in more detail. The antigen- and thapsigargin-mediated exocytosis in rat basophilic leukemia (RBL-2H3) cells were both inhibited by oxatomide. After aggregation of high affinity receptors for immunoglobulin E (Fc epsilon RI), protein tyrosine phosphorylation is induced. Oxatomide caused remarkable changes in the tyrosine phosphorylation pattern in resting cells. Also after antigen and thapsigargin activation, changes in the tyrosine phosphorylation of cellular proteins are observed. In addition, Ca2+ fluxes were studied by means of the net influx of 45Ca2+ and by measuring intracellular free Ca2+ concentrations ([Ca2+]) with the fluorescent probe fura-2. Oxatomide inhibited the 45Ca2+ influx and the increase in [Ca2+]i upon antigen and thapsigargin activation of the cells. Neither the release of Ca2+ from internal stores nor the efflux of Ca2+ over the plasma membrane seems to be affected. The effect of oxatomide on Ca2+ influx was further characterized by studying Ba2+ influx in the absence of extracellular free Ca2+. We conclude that inhibition of mediator release is mainly caused by inhibition of influx of extracellular Ca2+, via plasma membrane Ca2+ channels that are activated by depletion of intracellular Ca2+ stores. The molecular mechanism with which oxatomide might interfere with these channels is discussed.

Oxatomide and derivatives as inhibitors of mediator release from a mast cell model. Structure-activity relationships

A series of benzimidazolone and benzimidazole analogues of the antiallergic drug oxatomide (1-¿3-[4-(diphenylmethyl)-1-piperazinyl]propyl¿-1,3-dihydro-2H- benzimidazol-2-one, CAS 60607-34-3) [formula: see text], was evaluated for inhibiting the release of the performed mediator beta-hexosaminidase from the rat basophilic leukemia (RBL-2H3) cell line. Activation of the cells was induced by antigen, or by the calcium ionophore A23187 (calcimycin) in combination with or without the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). For the active compounds, inhibition of exocytosis was found with all triggers, with the antigen trigger being somewhat more sensitive. This indicates that the compounds influence several steps in the signal transduction route leading to exocytosis. The activity of the compounds is not totally aspecific as small structural changes strongly affect the inhibiting activity. Introduction of a chlorine substituent at the 6-position of the benzimidazolone group results in loss of activity. There does not seem to be a significant activity difference between the benzimidazolone and benzimidazole analogues. Analogues with n < 3, n > 5 or a branched alkyl chain between the piperazinyl and the benzimidazol(on)e moiety lose inhibitory activity. Secretion of the newly formed mediator arachidonic acid and its metabolites was affected by the compounds comparable to the effect on the release of beta-hexosaminidase. The anti-allergic activity did not correlate with the histamine H1-receptor antagonistic activity.

Inhibition of mediator release in RBL-2H3 cells by some H1-antagonist derived anti-allergic drugs: relation to lipophilicity and membrane effects

In a model for mucosal mast cells (RBL-2H3 cells) a set H1-antagonist derived anti-allergic drugs containing a diphenylmethyl piperazinyl moiety was examined for their ability to inhibit release of the mediator beta-hexosaminidase. Cells were activated with antigen or the calcium ionophore A23187, whether or not in combination with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Oxatomide, hydroxyzine and cetirizine inhibit the antigen induced beta-hexosaminidase release. The release triggered by A23187, whether or not in combination with TPA is hardly influenced by the compounds. A biphasic dependence of the inhibition of exocytosis in RBL cells on lipophilicity is observed with the optimum at log P is 5-6. The extremely lipophilic compounds meclozine and buclizine are not active in this model. pH dependence of the effect of the drugs shows that especially the uncharged species are active in inhibiting exocytosis. The investigated compounds show an effect on phase transitions in L-alpha-phosphatidylcholine dipalmitoyl liposomes as assayed with differential scanning calorimetry (DSC). For the less extremely lipophilic compounds the induced changes in the phospholipid membranes increased with lipophilicity. The relation between structural features of the drug and the interaction with phospholipids is discussed in view of the DSC results. We conclude that location of the active drugs at the membrane or the membrane/protein interface is important for the inhibiting activity on exocytosis. This could affect several membrane related processes, which are abundant in the early phases of the IgE-mediated signal transduction process.

Kinetic evaluation of the oxidation of phenothiazine derivatives by methemoglobin and horseradish peroxidase in the presence of hydrogen peroxide. Implications for the reaction mechanisms

The oxidation of ten 2-substituted 10-(3-(dimethylamino)propyl) phenothiazines (PHs) by methemoglobin (metHb) and horseradish peroxidase (HRP) in the presence of H2O2 was kinetically analysed based on an enzymic-chemical second-order reaction with substrate regeneration: PHs are oxidized enzymatically to their radical cations (PH+) which subsequently, in a second order reaction, react further to parent compound and PH-sulfoxide (PHSO). The enzymic reaction rate can be obtained from the accumulation curves of both radical cation formation and sulfoxide formation. In the case of chlorpromazine and promazine both methods gave similar reaction rates. The rate constant of PH+. decay could also be determined from the radical concentrations of their radicals. The rate constant of reaction of PHs with HRP compound II was also analysed. The logarithm of this rate constant correlated well with the Hammett sigma para and the Swain and Lupton F and R substituent constants, whereas no correlation with hydrophobic and steric parameters was found. This indicates that the interaction of PH with the porphyrin ring, which is the active site of HRP, is predominantly under electronic control. In the case of catalysis by hemoglobin (Hb), the formation of the reactive Hb form, ferry1Hb with a protein radical, appeared to be rate limiting in the oxidation of PHs by metHb-H2O2. Differences in the conversion rates of various PHs can be explained by a competition between their electron transfer reaction to the protein radical and the denaturation reaction(s) involving the protein radical. Our results confirm our earlier observation that the mechanism of oxidation by metHb-H2O2 differs from that of the classical peroxidases. In the former case, electron transfer from PH occurs most likely to a tyrosine residue on the globin part, whilst in the latter case electron transfer to the porphyrin moiety takes place.

The uptake of the trypanocidal drug suramin in combination with low-density lipoproteins by Trypanosoma brucei and its possible mode of action

In plasma, a significant part of suramin circulates in tight association with low-density lipoproteins (LDL). At therapeutically obtainable concentrations (100 microM) of suramin, about 85% of the total amount of the drug was bound to proteins, approximately 15% of which was bound to LDL. The molar ratio of suramin bound to LDL in serum was 7.5. The capacity of the high-affinity binding sites of LDL were 6.6 x 10(6) M-1, both in Tris buffer and in ultrafiltrate of serum. Suramin (100 microM) decreased the uptake of host LDL through receptor-mediated endocytosis by Trypanosoma brucei, with approximately 50%. LDL served as the only carrier for suramin uptake. Serum albumin, another important carrier for suramin in blood, was not able to promote suramin uptake, neither was delipidified plasma. The suramin taken up by T. brucei was recovered, in part, in the lysosomal fractions. It is suggested that deprivation of the parasite from cholesterol and phospholipids by an inhibition of the uptake of LDL, contributes to the mode of action of suramin, in addition to the many other effects that the drug may exert on the parasite. The toxic side-effects of suramin on the host are discussed in the light of its association with circulating lipoproteins.

Steroid binding to human serum albumin and fragments thereof. Role of protein conformation and fatty acid content

The binding properties of the steroids testosterone and pregnenolone to human serum albumin (HSA) and derived fragments of albumin have been investigated by means of equilibrium dialysis and circular dichroism. The 46 kDa peptic fragment (P46) of HSA comprises domains one and two of the HSA structure, whereas the other fragment, the 45 kDa tryptic fragment (T45) is composed of domains two and three. A comparison of the binding behaviour of the steroid ligands to HSA and its fragments showed that the single primary testosterone binding site in all probability is located in the second domain of the HSA molecule. For pregnenolone it was found that at least two primary binding sites are present, also located in domain two. Both steroids show pH dependent binding profiles in the case of HSA and the P46 fragment. The binding of the steroids to the T45 fragment seems to be pH independent. The same phenomenon was observed with the circular dichroism experiments, indicating a link between the steroid binding properties and the structural behaviour of the proteins. In fact, the binding properties of the steroids can be assigned to the neutral-to-base (N-B) transition. The possible role of fatty acids as modulators in the transport processes of steroids in the body is discussed.

The role of protein charge in protein-lipid interactions. pH-dependent changes of the electrophoretic mobility of liposomes through adsorption of water-soluble, globular proteins

The role of electrostatics in the adsorption process of proteins to preformed negatively-charged (phosphatidylcholine/phosphatidylglycerol) and neutral (phosphatidylcholine) liposomes was studied. The interaction was monitored at low ionic strength for a set of model proteins as a function of pH. The adsorption behavior of trypsin inhibitor (pI = 4.6), myoglobin (pI = 7.4), ribonuclease (pI = 9.6), and lysozyme (pI = 10.7) with preformed liposomes was investigated, along with changes in the electrophoretic mobility of liposomes through the adsorption of charged proteins. Mean protein charge was determined by acid/base titration. Significant adsorption of the proteins to negatively-charged liposomes was only found at pH values where the number of positive charge moieties exceeds the number of negative charge moieties on the protein by at least three charge units. Negligible adsorption to liposomes composed of zwitterionic lipids was observed in the pH range tested (4-9). The absolute value of the electrophoretic mobilities of negatively-charged, empty liposomes decreased after adsorption of positively-charged proteins. With increasing protein to phospholipid ratio, the drop in the electrophoretic mobility leveled off and reached a plateau; protein adsorption profiles showed a similar shape. Analysis of the data demonstrated that neutralization of the liposome charge due to the adsorption of the positively-charged proteins is the controlling factor in their adsorption. The plateau level reached depended on the type of protein and the pH of the incubation medium. This pH dependency could be ascribed to the mean positive charge of the protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Ramipril prevents impaired endothelium-dependent relaxation in arteries from rabbits fed an atherogenic diet

Endothelium-dependent relaxation in arteries is attenuated in clinical and experimental atherosclerosis. This study investigates the endothelial preservation properties of the angiotensin converting enzyme inhibitor, ramipril, by assessing its ability to restore endothelium-dependent responsiveness in blood vessels from rabbits fed an atherogenic diet (0.25% cholesterol; 3% coconut oil; 12 weeks). Seven rabbits fed the atherogenic diet received ramipril (3 mg/kg mixed into their food daily) and 6 rabbits were maintained on the atherogenic diet alone. Control rabbits (n = 6) were fed a standard diet and did not receive ramipril. At the end of the dietary intervention, the rabbits were killed and blood was collected for measurement of the lipid profile. The thoracic aorta was isolated and half was frozen for pathologic review while the other half was cut into rings and placed in a muscle bath for measurement of isometric force development. Dose response curves to phenylephrine (10(-9) to 10(-5) M) and angiotensin II (10(-10) to 3 x 10(-7) M) were completed. There was a minimal decrease in responsiveness to phenylephrine in vessels from rabbits eating the atherogenic diet compared with controls and no significant differences in the response to angiotensin II for any of the vessels. Following contraction by phenylephrine, acetylcholine (10(-9) to 10(-5) M) and nitroglycerin (10(-10) to 10(-5) M) dose response curves were completed. Relaxation to acetylcholine in aortic rings from control rabbits was observed, although in arteries from atherogenic rabbits relaxation was attenuated. This effect was prevented in the atherogenic rabbits fed ramipril. Responsiveness to the endothelium-independent vasodilator, nitroglycerin, was similar in arteries from the three rabbit groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of albumin on adenylate cyclase receptor-related signal transduction of human peripheral blood mononuclear cells

In the present study we investigated in vitro the effect of human serum albumin (HSA) on receptor-stimulated cAMP production in isolated human peripheral blood mononuclear cells (PBMC). The cAMP production is strongly correlated with the pH of the medium during long incubations with albumin. Adenylate cyclase is stimulated by receptor agonists like histamine, forskolin, prostaglandin E2 and the beta-adrenergic agonist isoprenaline, in the presence or absence of HSA. This protein, at concentrations above 0.1%, dose-dependently inhibits both basal and agonist-stimulated cAMP levels in PBMC. In the presence of 0.5% HSA a significant reduction of 30-60% (cell batch dependent) is induced, a reduction which is not incubation time dependent. Washing the cells after a period of incubation with 2% HSA does not reverse the HSA-induced cAMP inhibition. Oleic acid-evoked conformational changes in HSA were not capable of influencing the inhibition processes of HSA on the isoprenaline-stimulated cAMP production. Structure-controlled interactions between HSA and membrane or adenylate cyclase are therefore unlikely. Bovine serum albumin and chicken albumin had different effects upon the agonist-stimulated cAMP production as compared with HSA. At this moment no explanation for this behavior can be provided. The findings indicate that albumin may inhibit non-specifically cAMP production in PBMC and possibly influences membrane-controlled processes.

The stimulatory effect of albumin on luteinizing hormone-stimulated Leydig cell steroid production depends on its fatty acid content and correlates with conformational changes

The effects of purified albumin species and albumin fragments (0.2-1% w/v) on short-term (4 h) steroid secretion by immature rat Leydig cells, in the presence of a maximally stimulating dose of luteinizing hormone (LH), were investigated. Human albumin and the peptic fragment (comprising residues 1-387) enhanced pregnenolone production in isolated rat Leydig cells, whereas chicken albumin and the tryptic fragment (comprising residues 198-585) were not active. This stimulatory effect of human albumin and the peptic fragment correlated with the potential of these proteins to undergo a pH-dependent neutral-to-base transition as measured by circular dichroism. The tryptic fragment and chicken albumin did not have the potential to undergo such a transition. The pH-dependent conformational changes of albumin and fragments thereof occurred in parallel with a change in the binding affinity for testosterone and pregnenolone. The fatty acid oleic acid and the drug suramin, only when present in a molar ligand-to-albumin ratio equal to or higher than 2, inhibited the albumin-mediated stimulation of steroid production. These data show that the stimulatory effects of albumin species on LH-induced Leydig cell pregnenolone production depend on their fatty acid content and correlate with the potential of these molecules to undergo conformational changes. It is unknown via which mechanisms albumin exerts its stimulatory effect, but the LH action through the cyclic AMP pathway seems not to be affected.

Oxidation of chlorpromazine by methemoglobin in the presence of hydrogen peroxide. Formation of chlorpromazine radical cation and its covalent binding to methemoglobin

The oxidation of chlorpromazine by methemoglobin plus H2O2 has been studied. The transient formation of the chlorpromazine radical cation in this reaction has been demonstrated by light absorption measurements. Under the experimental conditions complete conversion of chlorpromazine yields approximately 60% chlorpromazine sulfoxide. From studies with 3H-labeled chlorpromazine it appears that the remaining 40% is covalently bound to apohemoglobin. Upon reaction of methemoglobin with H2O2 a stable ferrylhemoglobin is formed. This ferrylhemoglobin is not the reactive species, which accepts the chlorpromazine electron, as its presence is not sufficient to induce chlorpromazine oxidation. For this the presence of H2O2 is a prerequisite. This indicates that a transient species in the formation of the stable ferrylhemoglobin is involved, whether this is a compound I analogue or a ferrylhemoglobin with a free radical on one of the apoprotein residues. Exposition of methemoglobin to H2O2 denatures hemoglobin and induces protein-heme crosslinks, as appears from changes in the visible absorption spectrum and heme retention by the protein after methyl ethyl ketone extraction. Reaction with CPZ partly protects against denaturation and crosslinking.

Location and characterization of the suramin binding sites of human serum albumin

The objective of the present study was to investigate the location of the high-affinity suramin binding sites on the human serum albumin molecule. For this purpose, circular dichroism and equilibrium dialysis experiments were performed on the interaction between suramin and a large peptic and a large tryptic fragment of albumin, the former comprising domains one and two of the albumin structure and the latter domains two and three. The equilibrium dialysis experiments revealed that albumin and the fragments have a comparable total affinity for suramin. Furthermore, all three proteins display a similar pH dependence of the unbound fraction of suramin. The circular dichroism experiments revealed that only the suramin-albumin and the suramin-peptic fragment complexes can undergo the pH dependent neutral-to-base or N-B conformational change, whereas the suramin-tryptic fragment complex lacks this ability. It is likely that the main parts of the high-affinity binding sites for suramin are located in domain two of the albumin molecule. The nature of these binding sites is discussed. The deprotonation of histidine and other positively charged residues taking part in salt bridges between suramin and albumin is, in all probability, the main cause of the decrease in affinity of suramin for albumin as the pH is raised from 6 to 9.

Liver abscesses: successful treatment with choledochoduodenostomy

I have described two cases of hepatic abscess due to E coli after choledochoduodenostomy for choledocholithiasis, and have discussed the relationship between abscess formation and size of the anastomosis. I conclude that a small anastomosis may in some cases predispose to this problem. Treatment by percutaneous drainage of the abscess was successful in both cases.

Mechanism by which warfarin binds to human serum albumin. Stopped-flow kinetic experiments with two large fragments of albumin

In order to obtain information about the kinetics of the process by which warfarin binds to human serum albumin at a molecular level, we performed stopped-flow kinetic experiments on albumin and on a large peptic fragment (residues 1-387) and a large tryptic fragment (residues 198-585) of albumin. From these experiments it can be concluded that the first interaction between warfarin and the proteins is almost certainly diffusion-controlled and is dependent on the net charges of the reactants. The next step in the binding process involves the formation of an activated warfarin-protein complex, whereafter the final complex is formed. The warfarin-albumin complex forms more slowly than the warfarin-fragment complexes, because the formation is sterically hindered by the albumin structure. We think it very unlikely that albumin has an oblate ellipsoid structure; it is much more likely to have a U-shaped structure, where the domains make contact with each other. If this hypothesis is correct, then this indicates that the domains do not act independently of each other. The formation of the activated warfarin-albumin complex is further influenced by the conformational state of the albumin molecule, i.e. the N-B transition. The possible role of this N-B transition in albumin-mediated transport of drugs through cellular membranes is discussed.

The molecular mechanism of the neutral-to-base transition of human serum albumin. Acid/base titration and proton nuclear magnetic resonance studies on a large peptic and a large tryptic fragment of albumin

In order to obtain a better understanding of the neutral-to-base (N-B) transition of human serum albumin, we performed acid/base titration experiments and 500-MHz 1H NMR experiments on albumin and on a large peptic (residues 1-387) and large tryptic (residues 198-585) fragment of albumin. The acid/base titration experiments revealed that Ca2+ ions induce a downward pK shift of several histidine residues of the peptic (P46) fragment and of albumin. By contrast, Ca2+ has very little influence on the pK of histidine residues of the tryptic (T45) fragment. In albumin, the pH-dependent His C-2 proton resonances, observed with 1H NMR experiments, have been allotted the numbers 1-17. It proved possible to locate these resonances in the P46 and the T45 fragments. A correspondence was found between the number of histidines detected by the acid/base titration and by the 1H NMR experiments. The results of the experiments lead us to conclude that in domain 1 at least the histidines corresponding to the His C-2 proton resonances 1-5 play a dominant role in the N-B transition. The Cu2+-binding histidine residue 3 (resonance 8) of the albumin molecule is not involved in the N-B transition. In addition, we were able to assign His C-2 proton resonance 9 to histidine 464 of the albumin molecule. The role of the N-B transition in the transport and cellular uptake mechanisms of endogenous and exogenous compounds is discussed.

Location and characterization of the warfarin binding site of human serum albumin. A comparative study of two large fragments

The warfarin binding behaviour of a large tryptic fragment (residues 198-585 which comprise domains two and three) and of a large peptic fragment (residues 1-387 which comprise domains one and two) of human serum albumin has been studied by circular dichroism and equilibrium dialysis in order to locate and characterize the primary warfarin binding site. The induced ellipticity of the warfarin-peptic fragment complex turned out to be pH dependent. This pH dependence occurs in the region of the neutral-to-base transition of the albumin molecule. The induced ellipticity of the warfarin-tryptic fragment complex is pH independent. Difference CD-spectra showed that the peptic fragment and albumin have similar warfarin binding properties whereas the tryptic fragment has deviant warfarin binding properties. The equilibrium dialysis experiments showed that the affinity of warfarin to the peptic fragment and to albumin is practically the same whereas the affinity of warfarin to the tryptic fragment is a factor 2-8 lower than the affinity of warfarin to albumin. Our results indicate that the main part of the primary warfarin binding site is located in domain two of the albumin structure and that domain one plays an important role in the N-B transition of albumin.

Pharmacokinetics and safety of transcorneal iontophoresis of tobramycin in the rabbit

Transcorneal iontophoresis of tobramycin in normal eyes of New Zealand white rabbits was compared to an eye cup control and application of fortified topical drops. Iontophoresis was performed with 25 mg/ml of tobramycin at 0.8 mAmps for 10 or 5 min. The eye cup with 25 mg/ml of tobramycin was placed on the eye for 10 min without current. Topical fortified drops (13.6 mg/ml) were applied every half hour for 4 hr. Epithelium, stroma, and aqueous humor were assayed separately at 1, 4, 8 and 16 hr after treatment. The eyes were examined using the slit-lamp biomicroscope before and immediately after the treatment, and prior to sacrifice. Two eyes were examined by light and scanning electron microscopy 5 and 10 min after iontophoresis. Iontophoresis yielded significantly higher tobramycin concentrations than the eye cup or fortified topical drops at 1 hr and 4 hr after treatment (P = 0.001). In all treated eyes, iontophoresis resulted in epithelial edema and mucous discharge, which resolved by 24 hr after the treatment. Histologically there was evidence of epithelial disruption in the superficial layer after 5 min of iontophoresis and in all layers of the epithelium after 10 min of iontophoresis. Iontophoresis is a relatively safe, effective method to deliver medications to ocular tissues and may be useful alone or as an adjunct to current modes of antimicrobial chemotherapy.

Drug-binding and other physicochemical properties of a large tryptic and a large peptic fragment of human serum albumin

The diazepam-binding behaviour of a large tryptic and a large peptic fragment of human serum albumin has been studied by circular dichroism and equilibrium dialysis in order to locate the primary diazepam-binding site on the albumin molecule. The analytical set-up of the FPLC was used to find the optimum experimental conditions for isolating the fragments. Conventional columns with a 100-fold higher loading capacity than the analytical FPLC columns were used to isolate large amounts of the fragments. The isolation procedure for the tryptic fragment (45 kDa, domains two and three of the albumin structure) is described in this paper. The description of the isolation procedure for the peptic fragment (46 kDa, domains one and two of the albumin structure) is published elsewhere (Bos, O.J.M., Fischer, M.J.E., Wilting, J. and Janssen, L.H.M. (1988) J. Chromatogr. 424, 13-21). The induced ellipticity of the diazepam-fragment complexes as well as the affinity of diazepam to the fragments turned out to be pH dependent. This pH dependence occurs in the region of the neutral to base transition of the albumin molecule. Difference CD-spectra of the proteins showed that the tryptic fragment and albumin have similar diazepam-binding properties, whereas the peptic fragment has different diazepam-binding properties. This result is in line with our equilibrium dialysis experiments which showed that the affinity of diazepam to the tryptic fragment and to albumin is of the same order of magnitude, whereas the affinity of diazepam to the peptic fragment is several orders of magnitude lower. On the basis of these results, it can be concluded that the tryptic fragment contains the primary diazepam-binding site and the peptic fragment one or more secondary diazepam-binding sites. This means that at least the main part of the primary diazepam-binding site is located in domain three of the albumin structure.

Procedure for the isolation of a large peptic fragment of human serum albumin

For a thorough investigation of the drug-binding behaviour and other physicochemical properties of human serum albumin, one needs large amounts of specific fragments of albumin. Such fragments were obtained by careful proteolysis of the native protein with pepsin at pH 3.70. The fast protein liquid chromatographic technique was used to find the optimum experimental conditions for the separation of the fragments. By means of anion-exchange chromatography, chromatofocusing and gel permeation, it was possible to obtain a large fragment with a relative molecular mass of 46,000. The fragment could be assigned to segment 1-387 and therefore consists of domains 1 and 2 of the albumin structure. A 1-g amount of albumin produced 50 mg of a fragment that was 98% homogeneous.

A Merkel cell tumor of the eyelid

The Merkel cell is a distinctive nondendritic, nonkeratinocytic, epithelial clear cell believed to migrate from the neural crest to the epidermis and dermis, which is usually located in or near the basal layer of the epidermis and associated with nerve terminations. Merkel first described these cells in 1875 as "Tastzellen" occurring in the snout of a mole. They are believed to function as slowly adapting mechanoreceptors that mediate the sense of touch. Tumors arising from Merkel cells have been reported to occur on the head and neck area, the trunk, arms, and legs, and resemble a primary cutaneous lymphoma or cutaneous metastasis of a lymphoma or a carcinoma. Electron microscopy, to locate the characteristic membrane-bound, dense core neurosecretory granules, is needed for accurate diagnosis. These tumors must be treated aggressively to minimize the chance of local recurrence and nodal or visceral metastases. The authors present a case of Merkel cell tumor occurring on the eyelid. The clinical history, light and electron microscopic findings are shown.

Squamous cell carcinoma of the lacrimal sac

Diagnosis to differentiate successfully an uncommon epidermoid carcinoma of the lacrimal sac from the commoner acute inflammation of the lacrimal sac requires a good history and thorough physical examination. If epidermoid carcinoma of the lacrimal sac is suspected, additional procedures including a dacryocystogram, orbital tomograms, plain films and CAT scans, and otolaryngologic consultation are necessary. Such a successful diagnosis of an epidermoid carcinoma of the lacrimal sac is reported here. An aggressive surgical approach is described and strongly recommended because review of the literature shows that the prognosis for these tumors is very grave.