Zinc may regulate serum leptin concentrations in humans

OBJECTIVE

Leptin, the product of the ob gene, plays a key role in a feedback loop that maintains energy balance by signaling the state of energy stores to the brain and by influencing the regulation of appetite and energy metabolism. Zinc also plays an important role in appetite regulation. Thus, we evaluated the relationship between zinc status and the leptin system in humans.

METHODS

We studied nine healthy men with marginal zinc deficiency, induced by dietary means, before and after zinc supplementation.

RESULTS

Zinc restriction decreased leptin levels while zinc supplementation of zinc-depleted subjects increased circulating leptin levels. In addition, zinc supplementation increased IL-2 and TNF-alpha production that could be responsible for the observed increase in leptin concentrations.

CONCLUSIONS

Zinc may influence serum leptin levels, possibly by increasing the production of IL-2 and TNF-alpha.

Comparison of a prepCheck-supported self-assessment concept with conventional faculty supervision in a pre-clinical simulation environment

OBJECTIVES

This study aimed to evaluate the educational outcome of a digitally based self-assessment concept (prepCheck; DentsplySirona, Wals, Austria) for pre-clinical undergraduates in the context of a regular phantom-laboratory course.

MATERIALS AND METHODS

A sample of 47 third-year dental students participated in the course. Students were randomly divided into a prepCheck-supervised (self-assessment) intervention group (IG; n = 24); conventionally supervised students constituted the control group (CG; n = 23). During the preparation of three-surface (MOD) class II amalgam cavities, each IG participant could analyse a superimposed 3D image of his/her preparation against the "master preparation" using the prepCheck software. In the CG, several course instructors performed the evaluations according to pre-defined assessment criteria. After completing the course, a mandatory (blinded) practical examination was taken by all course participants (both IG and CG students), and this assessment involved the preparation of a MOD amalgam cavity. Then, optical impressions by means of a CEREC-Omnicam were taken to digitalize all examination preparations, followed by surveying and assessing the latter using prepCheck.

RESULTS

The statistical analysis of the digitalized samples (Mann-Whitney U test) revealed no significant differences between the cavity dimensions achieved in the IG and CG (P = .406). Additionally, the sum score of the degree of conformity with the "master preparation" (maximum permissible 10% of plus or minus deviation) was comparable in both groups (P = .259).

CONCLUSION

The implemented interactive digitally based, self-assessment learning tool for undergraduates appears to be equivalent to the conventional form of supervision. Therefore, such digital learning tools could significantly address the ever-increasing student to faculty ratio.

Serotyping of Proteus mirabilis clinical strains based on lipopolysaccharide O-polysaccharide and core oligosaccharide structures

The aim of this work was to serotype Proteus mirabilis urinary tract infection (UTI) strains based on chemically defined O-antigens with the use of two clinical collections from Sweden and Poland consisting of 99 and 24 UTI strains, respectively. A simple two-step serotyping scheme was proposed using enzyme immunoassay with heat-stable surface antigens of Proteus cells and immunoblotting with isolated lipopolysaccharides (LPSs). Using polyclonal anti-P. mirabilis rabbit antisera, 50 Swedish and 8 Polish strains were classified into serogroups O10, O38, O36, O30, O17, O23, O9, O40, O49, O27, O5, O13, O24, O14, and O33. From the Swedish strains, 10 belonged to serogroup O10 and five to each of serogroups O38, O36, and O9. Therefore, none of the O-serogroups was predominant. The majority of the serotyped clinical strains possess acidic O-antigens containing uronic acids and various acidic non-carbohydrate substituents. In immunoblotting, antisera cross-reacted with both O-antigen and core of LPSs. The core region of 19 LPSs bound a single serum, and that of 12 LPSs bound more than two sera. Following bioinformatic analysis of the available sequences, a molecular approach to the prediction of Proteus core oligosaccharide structures was proposed. The identification of the core type of P. mirabilis R110, derived from a serogroup O3 wild strain, using restriction fragments length polymorphism analysis of galacturonic acid transferase is shown as an example. In summary, the most frequent O-serogroups among P. mirabilis UTI stains were identified. The diversity of serological reactions of LPSs is useful for serotyping of P. mirabilis clinical isolates. A possible role of the acidic components of O-antigens in UTI is discussed.