Genetic Carriers and Genomic Distribution of cadA6—A Novel Variant of a Cadmium Resistance Determinant Identified in Listeria spp.

Listeria monocytogenes is a pathogen responsible for severe cases of food poisoning. Listeria spp. strains occurring in soil and water environments may serve as a reservoir of resistance determinants for pathogenic L. monocytogenes strains. A large collection of Listeria spp. strains (155) isolated from natural, agricultural, and urban areas was screened for resistance to heavy metals and metalloids, and the presence of resistance determinants and extrachromosomal replicons. Of the tested strains, 35% were resistant to cadmium and 17% to arsenic. Sequence analysis of resistance plasmids isolated from strains of Listeria seeligeri and Listeria ivanovii, and the chromosome of L. seeligeri strain Sr73, identified a novel variant of the cadAC cadmium resistance efflux system, cadA6, that was functional in L. monocytogenes cells. The cadA6 cassette was detected in four Listeria species, including strains of L. monocytogenes, isolated from various countries and sources—environmental, food-associated, and clinical samples. This resistance cassette is harbored by four novel composite or non-composite transposons, which increases its potential for horizontal transmission. Since some cadAC cassettes may influence virulence and biofilm formation, it is important to monitor their presence in Listeria spp. strains inhabiting different environments.     

Poly(chitosan-ester-ether-urethane) Hydrogels as Highly Controlled Genistein Release Systems

Polymeric hydrogels play an increasingly important role in medicine, pharmacy and cosmetology. They appear to be one of the most promising groups of biomaterials due to their favorable physicochemical properties and biocompatibility. The objective of the presented study was to synthesize new poly(chitosan-ester-ether-urethane) hydrogels and to study the kinetic release of genistein (GEN) from these biomaterials. In view of the above, six non-toxic hydrogels were synthesized via the Ring-Opening Polymerization (ROP) and polyaddition processes. The poly(ester-ether) components of the hydrogels have been produced in the presence of the enzyme as a biocatalyst. In some cases, the in vitro release rate of GEN from the obtained hydrogels was characterized by near-zero-order kinetics, without “burst release” and with non-Fickian transport. It is important to note that developed hydrogels have been shown to possess the desired safety profile due to lack of cytotoxicity to skin cells (keratinocytes and fibroblasts). Taking into account the non-toxicity of hydrogels and the relatively highly controlled release profile of GEN, these results may provide fresh insight into polymeric hydrogels as an effective dermatological and/or cosmetological tool.     

Sex typing and androgyny: further explorations of the expressive domain

Previous research by Bem has indicated that androgynous individuals of both sexes display "masculine" independence when under pressure to conform as well as "feminine" nurturance when interacting with a kitten. In contrast, sex-typed individuals were low in one or both of these behaviors. The two studies reported here were designed to replicate the low nurturance of the masculine male and to clarify the unexpected finding that feminine females were low in both independence and nurturance. In the first study subjects interacted with a human infant, and in the second study they listened to a lonely student. Taken together, the results of these two studies conceptually replicated the low nurturance of the masculine male and demonstrated that the low nurturance of the feminine female does not extend to her interaction with humans. Finally, evidence was presented in support of Spence, Helmreich, and Stapp's distinction between "androgynous" individuals, who are high in both masculinity and feminity, and "undifferentiated" individuals, who are low in both of these characteristics.     

Intraretinal foreign bodies

PURPOSE: To present our experience with the removal of intraretinal foreign bodies. MATERIAL AND METHODS: 9 intraretinal foreign bodies were removed by pars plana vitrectomy. Laser photocoagulation of the retina surrounding the foreign body was performed either before surgery or intraoperatively (endolaser). Pars plana vitrectomy with foreign body removal through the sclerotomy site with endomagnet and/or forceps was performed. In some cases fluid-gas exchange was done. RESULTS: The average follow-up period was 6.2 months. Seven of nine foreign bodies were magnetic and two were nonmagnetic. Five of seven magnetic foreign bodies had negative magnetic traction as the first surgical procedure. In these 9 eyes, final visual acuity was below 1/50 in 2 eyes and over 5/50 in 7 eyes. CONCLUSION: Pars plana vitrectomy should be the method of choice in removal of intraretinal foreign bodies.     

Microphotoluminescence and perfect ordering of SiGe islands on pit-patterned Si(001) substrates

We show that both the morphology and the optoelectronic properties of SiGe islands growing in the pits of periodically pre-patterned Si(001) substrates are determined by the amount of Ge deposited per unit cell of the pattern. Pit-periods (p) ranging from 300 to 900 nm were investigated, and Ge growth was performed by molecular beam epitaxy (MBE) at temperatures of 690 and 760?°C. The ordered SiGe islands show photoluminescence (PL) emission, which becomes almost completely quenched, once a critical island volume is exceeded. By atomic force and transmission electron microscope images we identify the transition from pyramid-shaped to dome-shaped islands with increasing p. Eventually, the nucleation of dislocations in the islands leads to PL quenching. Below a critical Ge coverage a narrowing and a blue shift of the PL emission is observed, as compared to islands grown on a planar reference area of the same sample.     

Experimental studies on the growth of cultured epithelium and endothelium of rabbit cornea exposed to low temperature

Three strains of Mycoplasma synoviae (MS) (Olson-WVU 1853, reported in 1956; and Massachusetts 9895 and 5044, respectively isolated in 1957 and 1972) were used for experimental inoculation of chickens to evaluate the various mycoplasma serologic tests. The MS plate agglutination and hemagglutination-inhibition (HI) tests were highly sensitive for detection of infection; reactions persisted for test periods extending to 63 weeks. Correlation between MS HI-tube and micro methods was good. HI titers were highest in sera from birds inoculated with strain 9895. All three strains produced cross-reactions with M. Gallisepticum (MG) plate antigens, which were detectable for 2 to 12 weeks following MS inoculation; strain 5044 produced the lowest percentage of cross-reactions. MG HI titers of 16 were observed occasionally in sera from all three group inoculated with strain 1853. It appears from these limited serologic studies in chickens that there may be antigenic differences among the three MS strains.     

Viscosity effects in square wave polarography polyethylene glycols—Cd2+, Tl+—system

In both the dc polarography and in the square wave polarography, the Stokes—Einstein—Ilkovi? equation connecting polarographic current and viscosity of the solution, is valid only in the case of monomeric solutions. In solutions of polymers, the polarographic diffusion current is higher than it would be expected from the macro-viscosity. The phenomenon is explained by the fact of micro-viscosity which is lower than macro one and controls the diffusion of small species like inorganic cations. They do not “see” long chains and coils of polymers. Paper discusses the phenomenon from different points of view: electrochemical (filling the gap in general application of square wave polarography) and physicochemical (diffusion of cations as a means of investigation of the structure of polymeric solutions). Conclusions of the paper are also important for radiation chemistry where discussion of diffusion of small species cannot be done in terms of macro-viscosity.