Negative SPR Signals during Low Molecular Weight Analyte Recognition.

Surface plasmon resonance (SPR) is a powerful technique for studying biomolecular interactions mainly due to its sensitivity and real-time and label free advantages. While SPR signals are usually positive, only a few studies have reported sensorgrams with negative signals. The aim of the present work is to investigate and to explain the observation of negative SPR signals with the hypothesis that it reflects major changes in ligand conformation resulting from target binding. We demonstrated that these negative unconventional signals were due to the negative complex (ligand/analyte) refractive index increment (RII) deviation from the sum of the RII of the individual entities which counterbalanced the theoretical increase of the signal triggered by the target recognition and the ligand folding. We also found that the conformation change of biomolecules can induce a negative or a positive complex RII deviation depending on its sequence and immobilization mode.

Influence of the SPR Experimental Conditions on the G-Quadruplex DNA Recognition by Porphyrin Derivatives.

Surface plasmon resonance (SPR) is a powerful technique to study the interactions of ligands with analytes and therefore a number of biosensor surfaces and injection methods have been developed so far. However, many experimental parameters can affect the interactions and consequently the affinity measurements. In particular, the interactions of positively charged analytes (often used for anionic nucleic acids targets) can be influenced by the sensing surfaces (e.g., negatively charged), leading to significant nonspecific interactions as well as regeneration problems. The aim of the present work is to investigate the effect of different parameters, including ionic strength, SPR biosensor (i.e., nature of the surfaces), and the injection method on the recognition of porphyrin G-quadruplex ligands. We demonstrate that the injection method does not influence the affinity whereas the ionic strength and the nature of the surface impact the recognition properties of the porphyrin for the G-quadruplex DNA. We also found that self-assembled monolayer coating surface presents many advantages in comparison with carboxymethylated dextran surface for SPR studies of G-quadruplex DNA/ligand interactions: (i) the electrostatic interaction with charged analytes is less important, (ii) its structure/composition is less sensitive to the ionic concentration and less prone to unspecific adsorption, (iii) it is easily homemade, and (iv) the cost is approximately 10 times cheaper.

Transphrenic dissemination of actinomycosis.

Thoracic actinomycosis is an uncommon disease and often presents difficulty in diagnosis. Two cases are presented in which thoracic actinomycosis produced fistulae between the thoracic and abdominal cavities. Surgical drainage and high dose penicillin for at least 4-6 months was the treatment of choice.

Going Dutch in nocturnal enuresis.

Based on several intervention programmes, a strategy for the treatment of nocturnal enuresis has recently been developed by an expert committee in the Netherlands. It consists of three parts. First, two structured interviews are given: one to differentiate between enuresis and incontinence and one to detect associated problems such as diurnal enuresis, constipation or behavioural problems. Secondly, a medical examination is made, confined to the inspection of the external genitalia and lower back, palpation of the abdomen and urine examination. Thirdly, the following guidelines for treatment at different age levels are applied: up to the age of 6 years no intervention is needed; between the ages of 6 and 8 years, lifting out of bed and/or the calendar method; between the ages of 8 and 12 years, enuresis alarm (if not successful, medication with desmopressin is prescribed for a restricted period of time), and ambulatory dry-bed training in a group setting may follow; over 13 years of age, clinical dry-bed training according to the Messer/Azrin method is advised. According to the expert committee, these guidelines offer sufficient possibilities to deal with the problem of nocturnal enuresis.

Vigabatrin in the treatment of infantile spasms.

The anti-epileptic effect of vigabatrin as a first choice therapy was investigated in 6 children suffering from infantile spasms (IS). All 6 children showed a reduction in seizure frequency. Three children became seizure-free within a period of 2 weeks. Because our results suggest "an all or nothing phenomenon", a period of 2 weeks may be sufficient to evaluate the efficacy of vigabatrin in untreated infants suffering from IS. We suggest to use vigabatrin as a first choice anti-epileptic drug in infants with IS.

[IgA deficiency: clinical ans immunological evaluation of 28 patients]. / IgA-deficiëntie: klinische en immunologische evaluatie van 28 patiënten.

Seventeen patients with total IgA deficiency and II with partial IgA deficiency were investigated. Symptoms associated with IgA deficiency were retrospectively studied, and the levels of other immunoglobulins were measured in blood and in saliva. The most important associated complaints were recurrent upper respiratory infections. More than 50% of the symptomatic patients recovered clinically, associated with a recovery of the IgA level or with compensatory humoral immunological mechanisms (such as elevated IgG subclasses or strongly positive secretory IgM). The necessary diagnostic procedures, follow-up of patients and families are described.

The influence of immunosuppressive treatment on immune responsiveness in vivo in kidney transplant recipients.

In this study, we have compared the influence of CsA and pred/aza on the immunocompetence in man. Therefore, kidney-transplant recipients were tested for their primary keyhole limpet hemocyanin and secondary (tetanus and KLH) humoral immune responses and their primary dinitrochlorobenzene and secondary (recall antigens) cellular immune responses. We demonstrate that primary immune responses are inhibited by CsA, whereas secondary immune responses are relatively resistant. Pred/aza therapy seems to inhibit all cellular immune responses, as we demonstrated before, as well as the primary humoral immune responses. Secondary humoral immune responses are only slightly affected by pred/aza. Our results provide a strong argument for starting immunosuppression with CsA, either with or without a low-dose pred.

Interleukin 6 (IL-6) in serum and urine of renal transplant recipients.

Hybridoma growth factor (HGF) is a 20-25 kD protein, supporting the growth of hybridoma cells in vitro and capable of replacing feeder cells. It was shown to be produced by human monocytes and a number of cultured cell lines. Recently, HGF was found to be identical to interferon-beta 2 or 26 kD protein and BSF-2, and was renamed interleukin 6 (IL-6). Using a sensitive bio-assay we were able to measure IL-6 activity in the serum and urine of healthy volunteers and renal transplant recipients. Low levels of IL-6 were present in the serum but not in the urine of healthy individuals. In contrast, both serum and urine of renal transplant recipients contained high levels of IL-6 directly after transplantation and during acute rejection episodes. On the basis of kinetic studies of the IL-6 response, it is concluded that serial measurement of IL-6, especially in urine, may be of value in monitoring renal transplant recipients. Moreover, the sensitivity of the bioassay will allow for detailed studies as to the biological significance of IL-6 in health and disease.