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Candida albicans, C. glabrata, C. parapsilosis, and C. tropicalis are able to form biofilms on virtually any biomaterial implanted in a human host. Biofilms are a primary cause of mortality in immunocompromised and hospitalized patients, as they cause recurrent and invasive candidiasis, which is difficult to eradicate. This is due to the fact that the biofilm cells show high resistance to antifungal treatments and the host defense mechanisms, and exhibit an excellent ability to adhere to biomaterials. Elucidation of the mechanisms of antifungal resistance in Candida biofilms is of unquestionable importance; therefore, this review analyzes both the chemical composition of biomaterials used to fabricate the medical devices, as well as the Candida genes and proteins that confer drug resistance.

The present study investigates the potential use of non-catalyzed water-soluble blocked polyurethane prepolymer (PUP) as a bifiinctional cross-linker for collagenous scaffolds. The effect of concentration (5,10,15 and 20%), time (4,6,12 and 24 h), medium volume (50,100,200 and 300%) and pH (7.4,8.2,9 and 10) over stability, microstructure and tensile mechanical behavior of acellular pericardial matrix was studied. The cross-linking index increased up to 81% while the denaturation temperature increased up to 12 °C after PUP crosslinking. PUP-treated scaffold resisted the collagenase degradation (0.167 ± 0.14 mmol/g of liberated amine groups vs. 598 ± 60 mmol/g for non-cross-linked matrix). The collagen fiber network was coated with PUP while viscoelastic properties were altered after cross-linking. The treatment of the pericardial scaffold with PUP allows (i) different densities of cross-linking depending of the process parameters and (ii) tensile properties similar to glutaraldehyde method.

This paper describes the preparation and characterization of water-soluble urethane oligomers bearing protected isocyanate groups. It also points out its ability to crosslink decellularized pericardium.

Nursing in rabbits occurs inside the nest with circadian periodicity. To determine the contribution of suckling stimulation in regulating such periodicity, we varied the size of the litters provided (1, 2, 4, or 6-8 pups). Nursing does, kept under a 14:10 (L:D) photoperiod, were continuously videotaped from parturition into lactation day 15. Although parturitions occurred throughout the day, a significant negative linear correlation (p < 0.0001; r = -0.68) was evident between time of delivery and time of nursing on lactation day 1, regardless of newborn number: longer intervals between these two events were seen in does delivering in the early morning than in those that gave birth late in the day. In rabbits suckling 6-8 pups, a Rayleigh analysis revealed that the population vector best describing their nursing pattern (across lactation days 1-15) had a phase angle = 58° (corresponding to solar time 0352 h and rho = 0.78; p < 0.001). In contrast, the nursing pattern of does nursing litters smaller than 6 pups did not show circadian periodicity; rather, mothers showed multiple entrances into the nest box throughout the day. Cluster analysis revealed that the main equilibrium point of intervals between suckling bouts shifted from 24 h (6-8 pups) to 6 h (4 and 2 pups) and to as low as 4 h with 1 pup. In the groups nursing 2, 4, or 6-8 pups, most nursing episodes were followed by food and water intake. Those mothers also showed self-grooming of the ventrum and nipples after nursing. The incidence of these behaviors was lower in does nursing 1 pup. In conclusion, nursing in rabbits spontaneously occurs with circadian periodicity, but it is largely modulated by a threshold of suckling stimulation.

The aims of the study were to evaluate the influence of culture media on biofilm formation by C. albicans, C. glabrata, C. krusei, and C. parapsilosis and to investigate the responses of sessile cells to antifungals and reactive oxygen species (ROS) as compared to planktonic cells. For biofilm formation, the Candida species were grown at different periods of time in YP or YNB media supplemented or not with 0.2 or 2% glucose. Sessile and planktonic cells were exposed to increasing concentrations of antifungals, H2O2, menadione or silver nanoparticles (AgNPs). Biofilms were observed by scanning electron microscopy (SEM) and quantified by the XTT assay. C. albicans formed biofilms preferentially in YPD containing 2% glucose (YPD/2%), C. glabrata in glucose-free YNB or supplemented with 0.2% glucose (YNB/0.2%), while C. krusei and C. parapsilosis preferred YP, YPD/0.2%, and YPD/2%. Interestingly, only C. albicans produced an exopolymeric matrix. This is the first report dealing with the in vitro effect of the culture medium and glucose on the formation of biofilms in four Candida species as well as the resistance of sessile cells to antifungals, AgNPs, and ROS. Our results suggest that candidiasis in vivo is a multifactorial and complex process where the nutritional conditions, the human immune system, and the adaptability of the pathogen should be considered altogether to provide an effective treatment of the patient.

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The use of the Beer−Lambert law in spectroscopy is the core of standard methods for determining a chromophore concentration in a solution. Its application requires an understanding about interaction of light with a colored solution and the use of light emission and light detection devices. We build here a simple electronic circuit formed of light-emitting diodes and lightdependent resistors that can be used for measuring chromophore concentrations during experiments focused on chemical kinetics: decolorizing of phenolphthalein in a basic solution, and reduction of methylene blue by ascorbic acid. From the chemical point of view, the goal is to determine experimentally the rate law. In addition, students understand, using inexpensive electronics, the basic design of a spectrophotometer to achieve successful measurements of absorbance.