Cross-linked iron dextran is an efficient oral phosphate binder in the rat

BACKGROUND

There is a need for alternative oral phosphate binders. In-vitro studies showed that iron(III)oxide-hydroxide-modified cross-linked dextran is a promising, insoluble phosphate-binding agent. The present study was designed to assess its in-vivo efficacy and safety in the rat.

STUDY, DESIGN AND METHODS

Iron(III)oxide-hydroxide modified dextran beads were mixed with normal rat feed in a proportion of 8% by weight. With this formula rats were fed for 4 weeks. A control group received the same diet without added phosphate binder. Samples of blood, urine, and faeces were taken from each animal before the phosphate binder was administered, 2 weeks later, and at the end of the examination period (day 29). Phosphate, calcium, iron were analysed in the blood samples. Calcium and phosphate concentrations were determined in the urine, phosphate, calcium, and iron concentrations in the excrements. Stability of the material in the duodenum was also simulated.

RESULTS AND CONCLUSIONS

The results demonstrate an excellent phosphate-binding capacity of the material and a good tolerance during the intestinal passage. No significant chemical or enzymatic degradation, histological alterations, or other treatment-related macroscopic findings were recorded. The present efficacy and toxicity study has shown effective phosphate binding with no toxicity and no iron release after ingestion of this novel phosphate binding agent. We propose clinical evaluation studies to assess whether similar efficacy and safety can be shown in humans.

The Western blot is a highly sensitive and efficient technique in diagnosing allergy to wasp venom

BACKGROUND

Diagnosis of allergy to wasp venom and decision to perform immunotherapy are based on the patient's history, along with skin and in vitro tests.

OBJECTIVE

Given the high prevalence of specific IgE also in non-allergic individuals, we evaluated the sensitivity and specificity of Western blots as a possible alternative to serum analyses of venom-specific IgE.

METHODS

Skin prick and/or intracutaneous tests were performed in 30 patients with allergy to wasp venom (generalized reaction following sting) along with serum analysis of venom-specific IgE (AlaSTAT microplate) and Western blots. Western blots were subsequently scanned and evaluated qualitatively and semiquantitatively by means of densitometry. Bands were scored 'positive' in cases of signal intensities beyond the mean plus 3 standard deviations of control sera. Twenty newborns (age 2-7 days) and 30 adults without systemic or increased local reactions to hymenoptera stings served as controls.

RESULTS

Western blot sensitivity reached 100% in the samples studied and was thus superior to the sensitivities of serum analysis of venom-specific IgE using AlaSTAT microplate assay (90%) and skin tests (87%). The sensitivity of detection of a phospholipase A1 and antigen 5-specific band was higher compared with a hyaluronidase-specific band (97%, 97% and 86%, respectively). Twenty-four out of twenty-nine (83%) patients exhibited specific IgE antibodies against at least three distinct allergens. With regard to the specificities, skin tests as well as AlaSTAT microplate assays were comparable (90% and 93%, respectively), whereas the specificity of the Western blots was 70% if the appearance of any single band was regarded as a positive result. However, when analysing the appearance of a specific band for antigen 5 or hyaluronidase the specificity and overall diagnostic value increased markedly, making it the most efficient test (specificity 97% and 100%, efficiency 96.8% and 93.2%, respectively).

CONCLUSION

As allergy to wasp venom is a severe and potentially life threatening disease, false-negative test results need to be minimized. Therefore, the superiority of the Western blot with regard to sensitivity, specificity and overall efficiency makes this technique a valuable tool for its diagnosis.

Testing for thermal acclimation in zoospores of an amphibian pathogen

Thermal acclimation effects on locomotory performance have been widely documented for macroscopic organisms, but such responses remain largely unexplored in microorganisms. Metabolic theory of ecology (MTE) predicts faster responses in smaller organisms, with potential consequences for host-parasite interactions in variable temperature environments. We investigated thermal acclimation effects on zoospores of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd), quantifying (1) thermal performance for maximum zoospore velocity and (2) high temperatures needed to immobilize 50% (CT50max) or 100% (CT100max) of zoospores. We obtained measurements within 18 min following a temperature shift. We found significant curvilinear acclimation effects on maximum zoospore velocity and CT50max, although the latter pattern might have been driven by confoundment with zoospore density. We also observed a significant positive effect of the trial start temperature on CT50max, consistent with a rapid acclimation response to the start temperature on a time scale of ~1-6 min (i.e. too rapid for our experimental acclimation treatments to detect), implying that zoospores either have constitutive heat tolerance (i.e. no acclimation) or fully acclimate CTmax to new temperatures within ~10 min. To explore the plausibility of such a rapid response, we analyzed published CTmax acclimation times for macroscopic eukaryotes, resulting in a predicted interquartile range of 3.11-25.98 min when mass-scaled to the size of a Bd zoospore. Taken together, these results suggest that Bd zoospores do exhibit thermal acclimation response on the rapid time scale predicted by MTE, possibly giving Bd an advantage over slower-acclimating hosts in variable-temperature environments.

Characterization and extracorporeal application of a new phosphate-binding agent

A new phosphate-binding agent which does not cause any severe side effects in vivo was developed by modifying a crosslinked dextran with polynuclear iron(III)oxide-hydroxide. Its particle size ranges from 150 to 300 microns, and the iron content was about 18% by dry weight. The oxidation state of iron was characterized by ESCA and Mössbauer spectroscopy. The maximum phosphate binding capacity of the iron(III)oxide-hydroxide-modified dextran was determined with respect to aqueous phosphate solutions, human serum and whole blood. The effects on whole blood count, haemolysis, protein concentration and enzyme activities were examined. In addition, the influence of phosphate concentration, pH and temperature on the phosphate uptake of the material was determined. The results show that this new adsorbent might provide an alternative to conventional phosphate-binding agents. This paper also describes the first experiments on the therapeutic application of the material in an extracorporeal blood perfusion system for the treatment of hyperphosphataemia during haemodialysis.

Dynamic effects of thermal acclimation on chytridiomycosis infection intensity and transmission potential in Xenopus laevis

The pandemic amphibian pathogen Batrachochytrium dendrobatidis (Bd) can cause more severe infections with variable temperatures owing to delays in host thermal acclimation following temperature shifts. However, little is known about the timing of these acclimation effects or their consequences for Bd transmission. We measured how thermal acclimation affects Bd infection in Xenopus laevis, using a timing-of-exposure treatment to investigate acclimation effect persistence following a temperature shift. Consistent with a delay in host acclimation, warm-acclimated frogs exposed to Bd immediately following a temperature decrease (day 0) developed higher infection intensities than frogs already acclimated to the cool temperature. This acclimation effect was surprisingly persistent (five weeks). Acclimation did not affect infection intensity when Bd exposure occurred one week after the temperature shift, indicating that frogs fully acclimated to new temperatures within 7 days. This suggests that acclimation effect persistence beyond one week post-exposure was caused by carry-over from initially high infection loads, rather than an extended delay in host acclimation. In a second experiment, we replicated the persistent thermal acclimation effects on Bd infection but found no acclimation effects on zoospore production. This suggests that variable temperatures consistently exacerbate individual Bd infection but may not necessarily increase Bd transmission.