Biological effects of non-ionizing radiations: Cellular properties and interactions

The Lauriston Taylor lectures honor the founder of the National Committee on Radiation Protection and Measurement soon to be followed by the corresponding international organization. These standard setting bodies had a vast influence on proper recognition of radiation hazards. The 10th Taylor lecture is the first to deal with nonionizing radiations and may be, therefore, of particular interest to the bioengineer. During early history biophysics and bioengineering were primarily concerned with ionizing radiation bioeffects and electrophysiology. The nonionizing part of the radiation field and electrophysiology are closely related. Biomedical observation, biophysical and bioengineering efforts in the nonionizing radiation field are defined and complement each other. Topics concentrate on the relevant biophysical and bioengineering efforts of the author and his colleagues. They include: electrical properties of biological systems; established electrical field interactions (excitation, macromolecular responses and cellular responses); problems of dosimetry (macroscopic and microscopic considerations); conclusions about relative merits of various research approaches. Editor’s Note: By special permission from the National Council on Radiation Protection and Measurements, 7910 Woodmont Ave., Bethesda, MD, 20814, Mr. W. Roger Ney, Executive Secretary. Presented April 2, 1986 in the Auditorium of the National Academy of Sciences Building, Washington, DC.     

Hybrid intravenous digital subtraction angiography of the carotid bifurcation

A hybrid digital subtraction angiography technique and noise-reduction algorithm were used to evaluate the carotid bifurcation. Temporal, hybrid, and reduced-noise hybrid images were obtained in right and left anterior oblique projections, and both single- and multiple-frame images were created with each method. The resulting images were graded on a scale of 1 to 5 by three experienced neuroradiologists. Temporal images were preferred over hybrid images (average score = 3.2 and 2.4, respectively). The percentage of nondiagnostic examinations, as agreed upon by two readers, was higher for temporal alone than temporal + hybrid (4 and 1, respectively). In addition, also by agreement between two readers, temporal + hybrid images significantly increased the number of bifurcations seen in two views (87%) compared to temporal subtraction alone (64%).     

Atrophy of the residual alveolar ridge following tooth loss in an historical population

Oral Diseases (2010) 17 , 33–44 Objectives: To study the natural aetiopathology of jaw atrophy after tooth loss, unaltered by prosthetic procedures, an historical population without modern dental treatment was examined. Methods: Based on the hypothesis that there are predictable changes in shape during jaw‐atrophy, frequency and degree of atrophy as well as clinical aspects of bone quality and resorption were determined in the skeletal remains of 263 individuals. The potential association between age and frequency/severity of atrophy was analysed. Results: Atrophy in at least one jaw segment was present in 45.2% of the analysed jaw specimens. The residual ridge underwent a series of changes in shape and height following the pattern of resorption described for modern populations. The severity of these alterations was associated with the age of the individual and the region within the jaw. Atrophy was frequently related to structural degradation of the covering cortical layer. Conclusions: These findings prove that atrophy of the jaw evidently does occur, displaying similar patterns of resorption in a population without modern prosthetics, where the negative effect of ill‐fitting dentures is excluded. The basic information about alterations of shape and the cortical layer covering the residual crest might help to provide a deeper insight into aetiopathological mechanisms of this common oral disease.     

Misuse of Alcohol among Methadone Patients

Between 5 and 49% of patients undergoing methadone maintenance treatment (MMT) consume alcohol. They show less willingness to comply with treatment and are less committed, their treatment times are longer, and their observance is weaker. Alcohol misuse is the main cause of their increased mortality and morbidity rates. We conducted a multivariate, prospective, open‐label study in two groups of methadone patients: the first suffered from alcohol use disorder according to the criteria of the alcohol use disorder test (AUDIT), while the second was alcohol‐abstinent. In the process, we completed evaluations on the Toronto alexithymia scale, together with a self‐esteem inventory and a temperament and character inventory (TCI‐R). Our study included 152 patients, 27.6% of whom were high‐risk consumers. Comparison of the alcohol high‐risk consumers group and the low‐risk consumers showed that the former had higher rates of alexithymia, weaker self‐esteem, and lower scores of self‐directedness.     

Virulence Genes and Genotypic Associations in Nasal Carriage,Community-Associated Methicillin-Susceptible and Methicillin-Resistant USA400 Staphylococcus aureus Isolates

It is not well understood why strains of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), a major cause of skin and soft tissue infections, became successful so quickly, overtaking the place of methicillin-sensitive S. aureus (MSSA) in many communities. To evaluate the genetic basis of differences in their virulence traits, 293 S. aureus isolates consisting of three cohorts, genotypically defined clinical CA-MRSA (n = 77), clinical MSSA (n = 103), and nasal carriage MSSA (n = 113), collected over a 19-year period in two Midwestern states in the United States, were (i) extensively genotyped and (ii) screened for 40 known virulence genes which included those for enterotoxins, leukocidins, hemolysins, and surface proteins and several newly identified putative toxin genes from the USA400 lineage of CA-MRSA. Genotypically, nasal carriage and clinical MSSA isolates were much more diverse than was the CA-MRSA group, which was found to be of USA400 lineage only. Virulence gene profiles of the three groups showed that CA-MRSA strains harbored significantly higher percentages (≥95%; P value, <0.05) of the sea, sec, sec4, seg2, seh, sek, sel, sel2, ear, ssl1, lpl10, lukSF-PV, lukD, lukE, and clfA genes than did the carriage and the clinical MSSA group (range, 0% to 58%). Genes of the enterotoxin gene cluster, seg, sei, sem, sen, and seo, were present in the clinical and carriage isolates but not in the CA-MRSA group. These results suggest that the presence of additional virulence factors in USA400 CA-MRSA strains compared to the nasal carriage and clinical MSSA strains probably contributed to their enhanced virulence.Staphylococcus aureus both is a benign commensal and common pathogen in humans and is responsible for a variety of infections, ranging from superficial skin and soft tissue infections to bacteremia, endocarditis, and osteomyelitis (33). Based on its susceptibility to beta-lactams, S. aureus is commonly described as methicillin-susceptible S. aureus (MSSA) or methicillin-resistant S. aureus (MRSA) (15). Infections due to health care-associated MRSA (HA-MRSA) have been a problem since the 1970s; however, starting in the 1990s, new strains of MRSA, referred to as community-associated MRSA (CA-MRSA), appeared in community dwellers and were genetically different from HA-MRSA strains (7). Until recently, individuals who presented with infections due to CA-MRSA typically have had none of the established risk factors associated with HA-MRSA, such as recent hospitalization, surgery, dialysis, long-term care residence, or indwelling medical devices. Lately however, CA-MRSA strains have been reported from both the community and the health care settings (25, 45). Genotyping tools such as pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and spa typing have helped in distinguishing the genotypes of CA-MRSA strains from those of other S. aureus strains (2, 14, 26). In PFGE, SmaI-restricted S. aureus genomes are compared to determine their genetic relatedness and also compared against the reference USA genotypes (USA100, USA200, etc., up to USA1200) as described by the Centers for Disease Control and Prevention (CDC) (34, 53). Of these, CA-MRSA isolates mostly belong to USA300 and USA400 clones and in some cases USA1000 and USA1100 clones as well. HA-MRSA isolates generally belong to USA100, USA200, and USA500 (34, 35). One of the two major clones of CA-MRSA, USA400, recognized in the early 1990s and initially referred to as the MW2 clone, was the predominant CA-MRSA clone that initially circulated in the midwestern United States in the 1990s (8, 17, 40, 52). The second and more recent CA-MRSA clone, USA300, was first recognized in 2000 and has since spread throughout the world (54). More than a thousand MLST allelic profiles for S. aureus have been identified so far, of which CA-MRSA strains are primarily represented by sequence type 1 (ST1) (USA400) and ST8 (encompasses USA300 and USA500). Of the several thousand spa types in the Ridom database (http://spaserver.ridom.de/), the most predominant CA-MRSA spa types are t008 and t128.CA-MRSA strains, besides their distinct PFGE, ST, and spa profiles, almost ubiquitously possess the Panton-Valentine leukocidin (PVL or lukSF-PV) genes, in contrast to only 1% to 5% of S. aureus strains overall having these genes (33, 50, 57). The PVL toxin has been implicated in many skin and soft tissue infections and lethal necrotizing pneumonia, but the exact role of PVL during S. aureus infections remains controversial (10, 28, 31, 58). The genome sequence of the CA-MRSA strain MW2 of the USA400 lineage showed the presence of several additional putative toxin genes (e.g., ear, sec4, sel2, seg2, ssl1 [set16], and lpl10) compared with other S. aureus strains that had been sequenced (1). Some of these toxin genes share homology with classic staphylococcal enterotoxin genes that encode pyrogenic exotoxins (49) typically produced during the post-exponential phase of growth, and the genes encoding these exotoxins are most often carried on plasmids, bacteriophages, or pathogenicity islands. The classic staphylococcal enterotoxin genes (sea, seb, sec, sed, see, seg, seh, sei, sej, sek, sel, sem, sen, and seo) are commonly found in strains of S. aureus (12, 23, 39, 42, 43, 46, 62). Pyrogenic exotoxin genes are common in S. aureus, and as many as 73% of S. aureus isolates carry at least one of the genes encoding a classic pyrogenic exotoxin; however, the distribution among various clonal types differs (3). Strains of USA400 CA-MRSA typically have been shown to possess the sea, sec, seh, and sek enterotoxin genes, whereas HA-MRSA strains usually carry the sed, seg, sei, sej, sem, sen, and seo enterotoxin genes (40). Currently, the distribution of the newly identified putative toxin genes (seg2, sel2, sec4, ssl1, and lpl10) (1) from the MW2 strain has not been reported from among CA-MRSA strains in general or from clinical and nasal carriage MSSA strains. Since CA-MRSA isolates are able to cause disease in humans without predisposing risk factors and have spread rapidly in communities, these strains may possess a greater number of toxin genes than do the other strains of S. aureus.The aim of this study was to compare the genotypes of clinical CA-MRSA USA400, clinical MSSA, and colonizing nasal carriage MSSA isolates and determine the frequency and distribution of the classic enterotoxin genes as well as the new putative toxin genes in them. Our results showed that MSSA strains were much more diverse in their genotypes than were CA-MRSA USA400 strains. In addition, CA-MRSA USA400 strains possessed a distinct array of toxin genes compared to MSSA strains. These data may provide insight into the success of CA-MRSA USA400 and its ability to cause severe disease in previously healthy people.