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.

Adaptation in retinal rods of axolotl: intracellular recordings.

Intracellular recordings of the late receptor potential from rods of isolated axolotl retinas revealed the existence of a dark adaptation mechanism that is independent of rod pigment regeneration. Response amplitude of individual rods was measured as a function of intensity both before and at various times after exposure to bleaching illumination. The rod sensitivity increased by at least 3 to 4 log units during a period of 15 to 25 minutes following the bleach. During this time rod pigment regeneration was either too small to be measured or was nonexistent in our preparation.

Induction of melanized cells from a goldfish erythrophoroma: isolation of pigment translocation variants.

Melanization was induced in some cells of a goldfish tumor cell line (GEM-81) by cultivating the cells in autologous serum. The melanized cells continued to proliferate in vitro and several clones were isolated that differed with respect to cell morphology and intracellular distribution of pigment. Some of the clones consisted of cells able to translocate their melanosomes in response to epinephrine, melatonin, or adenosine 3', 5'-monophosphate.

Combined effects of heat, nisin and acidification on the inactivation of Clostridium sporogenes spores in carrot-alginate particles: from kinetics to process validation.

Combined effects of mild temperatures, acidification and nisin on the thermal resistance of Clostridium sporogenes ATCC 11437 spores were assessed. Inoculated carrot-alginate particles were used as a solid-food model for the validation of the spore inactivation during the flow of a solid-liquid food system through the holding tube of an aseptic processing unit. Inactivation kinetics was studied in a water bath with the spores inoculated into carrot-alginate particles and in Sorensen's phosphate buffer. For temperatures of 70-90 degrees C, D-values in the buffer were 24.9-5.7 min, much lower than those evaluated for the particles (115.1-22.2 min). Statistical analyses showed significant synergistic effects of temperature and pH on spore inactivation for both media. Acidification reduced the heat resistance of the spores by reducing the D-values. Nisin was not significantly effective at the lower concentrations (up to 750 IU/g). The combination of 90 degrees C, pH: 4.5 and 500IU/g nisin resulted in a ten-fold decrease of the D-value for spores inoculated in the particles (from 111.1 to 10.6 min). Microbial validation tests were conducted using a pilot-scale aseptic processing unit with a mixture of carrot cubes (10%) and carrier liquid of 2%-carboxymethylcellulose solution (90%). Spore-inoculated carrot-alginate particles (initial counts of 106 CFU/g, obtained after come-up-time pre-heat) with pH 3.5 and 2000 IU/g nisin were processed at 90 degrees C in the aseptic processing unit. Microbial analysis showed no spore survivors in the particles after passing through the holding tube (5.2-6.0 min of residence time). The proposed combination of these hurdles significantly enhanced the spore inactivation rate (D(90)=1.17 min) as compared to that for thermal treatment only (D(90)=19.6 min).

Upper esophageal stenosis: two case reports.

Esophageal stenosis caused by an intrinsic congenital deformity is uncommon in infants and children. The main forms of stenosis are congenital esophageal web congenital stricture caused by tracheobronchial remnants, and congenital idiopathic muscular hypertrophy. The authors report on two patients who were successfully treated and managed after being diagnosed as having upper esophageal stenosis. One patient underwent resection of the web and primary anastomosis of the esophagus and was discharged 6 days after surgery. After 1 year, this patient has had no symptoms of dysphagia or other postoperative difficulties. The second patient underwent balloon dilatation of the esophageal stricture and was discharged on the day of surgery; however, this patient required numerous repeat dilatations.