Patterns of care of radiotherapy in México

Aim

This survey is performed to learn about the structure of radiotherapy in México.

Background

Radiation oncology practice is increasing because of the higher incidence of cancer. There is no published data about radiotherapy in México.

Materials and methods

A questionnaire was sent to the 83 registered centers in the database of the Mexican regulatory agency. One out of the 32 states has no radiotherapy. 27 centers from 14 states provided their answers.

Results

829 patients are treated annually with any radiotherapy modality in each center. Two centers have one cobalt machine, 7 have a cobalt and a linac and 10 have more than one linac. Five centers use 2D planning systems, 22 use 3D; 9, conventional simulators; 22, CT based simulation, and 1 center has no simulation. Most of the centers verify beams with films, electronic portal image devices and cone beam CTs are also used. Intensity modulated and image guided radiotherapy are performed in 5 states. Breast, prostate, cervix, lung, rectum and head and neck cancer are the six most common locations. There are 45 public and 38 private centers, 2 dedicated to children. Two gamma knife units, 5 Novalis systems, 1 tomotherapy and 2 cyberknife machines are working. All centers have at least one radiation oncologist, one physicist and one radiotherapist.

Conclusions

Definitive conclusions cannot be drawn from this limited feedback due to a low participation of centers. This survey about radiotherapy in Mexico shows the heterogeneity of equipment as well as medical and technical staff in the whole country.     

Climate change effects on above- and below-ground interactions in a dryland ecosystem

Individual species respond to climate change by altering their abundance, distribution and phenology. Less is known, however, about how climate change affects multitrophic interactions, and its consequences for food-web dynamics. Here, we investigate the effect of future changes in rainfall patterns on detritivore–plant–herbivore interactions in a semiarid region in southern Spain by experimentally manipulating rainfall intensity and frequency during late spring–early summer. Our results show that rain intensity changes the effect of below-ground detritivores on both plant traits and above-ground herbivore abundance. Enhanced rain altered the interaction between detritivores and plants affecting flower and fruit production, and also had a direct effect on fruit and seed set. Despite this finding, there was no net effect on plant reproductive output. This finding supports the idea that plants will be less affected by climatic changes than by other trophic levels. Enhanced rain also affected the interaction between detritivores and free-living herbivores. The effect, however, was apparent only for generalist and not for specialist herbivores, demonstrating a differential response to climate change within the same trophic level. The complex responses found in this study suggest that future climate change will affect trophic levels and their interactions differentially, making extrapolation from individual species'' responses and from one ecosystem to another very difficult.     

In vitro propagation and cryopreservation of Romanian endemic and rare Hypericum species

Efficient micropropagation and cryopreservation of Hypericum richeri ssp. transsilvanicum, an endemic species in Romania, and Hypericum umbellatum, a rare and endangered Daco-Balkan species, was achieved. The effects of type of explant and cytokinin on in vitro plant regeneration were investigated. Shoot organogenesis was achieved in all explants, but stem nodes regenerated best. Organogenesis from nodal segments was promoted by incubating these explants on Murashige and Skoog (MS) medium in the presence of cytokinins (6-benzyladenine, thidiazuron, kinetin or 6-??,??-dimethylallylaminopurine), each tested at four concentrations. The best morphogenic response for both Hypericum species (number of shoots per explant, shoot length, axillary branching of shoot, and frequency of shoot organogenesis) was observed when explants were incubated on MS medium containing 0.44 or 1.11???M 6-benzyladenine. Root induction was achieved only when regenerated shoots were transferred to fresh medium with or without auxin. Maximum rooting was recorded on MS medium supplemented with 2.45???M indole-3-butyric acid. Plantlets grown in vitro were successfully acclimatized in the greenhouse and showed normal development. Shoot tips and axillary buds excised from the in vitro regenerated plants were successfully cryopreserved in liquid nitrogen by the droplet-vitrification method. Following preculture in 0.25?M sucrose, dehydration and cryopreservation, the highest regeneration rates were obtained in both species by using axillary buds (68?% for H. richeri ssp. transsilvanicum and 71?% for H. umbellatum).     

Hydrogen bonding in a model bacteriochlorophyll-binding site drives assembly of light harvesting complex

In this study, the contribution of intramembrane hydrogen bonding at the interface between polypeptide and cofactor is explored in the native lipid environment by use of model bacteriochlorophyll proteins. In the peripheral antenna complex, LH2, large portions of the transmembrane helices, which make up the dimeric bacteriochlorophyll-binding site, are replaced by simplified, alternating alanine-leucine stretches. Replacement of either one of the two helices with the helices containing the model sequence at a time results in the assembly of complexes with nearly native light harvesting properties. In contrast, replacement of both helices results in the loss of antenna complexes from the membrane. The assembly of such doubly modified complexes is restored by a single intramembrane serine residue at position -4 relative to the liganding histidine of the alpha-subunit. In situ analysis of the spectral properties in a series of site-directed mutants reveals a critical dependence of the model complex assembly on the side chain of the residue at this position in the helix. A hydrogen bond between the hydroxy group of the serine and the 13(1) keto group of one of the central bacteriochlorophylls of the complexes is identified by Raman spectroscopy in the model antenna complex containing one of the alanine-leucine helices. The additional OH group of the serine residue, which participates in hydrogen bonding, increases the thermal stability of the model complexes in the native membrane. Intramembrane hydrogen bonding is thus shown to be a key factor for the binding of bacteriochlorophyll and assembly of this model cofactor-polypeptide site.     

Plant regeneration from Rosa shoot tips cryopreserved by a combined droplet vitrification method

Shoot tips obtained from in vitro Rosa plants (three cultivars) were successfully cryopreserved by a combined droplet vitrification method and subsequently shoots regenerated. The excised shoot tips (1–4 mm long) were incubated in a liquid MS medium supplemented with 2.5 mg l⁻¹ thiamine, 0.2 mg l⁻¹ biotin, 0.2 mg l⁻¹ pyridoxine, 0.25 mg l⁻¹ 6-benzylaminopurine (BAP), 0.5 mg l⁻¹ gibberellic acid (GA₃) and 0.08 M sucrose, for 24 h. Following that incubation shoot tips were pre-cultured in this MS medium containing 0.1 till 1.0 M sucrose for 24 and 48 h, respectively. Pre-cultured shoot tips were dehydrated with concentrated PVS2 cryoprotective solution for 10–30 min at room temperature, prior to a direct plunge in liquid nitrogen. After rapid rewarming in the above mentioned liquid medium shoot tips were plated on a modified MS medium (5 g l⁻¹ agar) supplemented with vitamins and plant growth regulators as mentioned above for regrowth. Cryopreserved shoot tips resumed growth within 10 days and regenerated shoots within 3 weeks. The highest numbers of regrowing shoot tips were 64.44% for cv. Kardinal, 67.73% for cv. Fairy and 57.57% for cv. Maidy.     

Fungal Olecranon Bursitis in an Immunocompetent Patient by <Emphasis Type="Italic">Knoxdaviesia dimorphospora</Emphasis> sp. nov.: Case Report and Review

Bursitis is a common medical condition that can occur either with or without infection. We present a case of fungal olecranon bursitis in an immunocompetent individual caused by the new species Knoxdaviesia dimorphospora. It is a dematiaceous filamentous fungus characterized by the production of two different conidia: hyaline and cylindrical, which rise up from phialidic conidiogenous cells located in the upper part of differentiated and unbranched conidiophores, and pale brown and ellipsoidal conidia produced by phialidic conidiogenous cells which are born directly on hyphae. In addition to its morphological peculiarities, the novelty of the fungus was confirmed by sequence analysis of the internal transcribed spacer (ITS) regions and D1/D2 domains of the 28S of the nuclear rRNA gene. The fungal infection was confirmed by cytological examination and repeated cultures. The infection was resolved by surgical debridement and drainage, and the patient presented a complete functional recovery 3 months later. The in vitro antifungal susceptibility to this new human opportunist is provided, terbinafine being the drug with the most potent activity.     

Induction of Prophages by Fluoroquinolones in Streptococcus pneumoniae: Implications for Emergence of Resistance in Genetically-Related Clones

Antibiotic resistance in Streptococcus pneumoniae has increased worldwide by the spread of a few clones. Fluoroquinolone resistance occurs mainly by alteration of their intracellular targets, the type II DNA topoisomerases, which is acquired either by point mutation or by recombination. Increase in fluoroquinolone-resistance may depend on the balance between antibiotic consumption and the cost that resistance imposes to bacterial fitness. In addition, pneumococcal prophages could play an important role. Prophage induction by fluoroquinolones was confirmed in 4 clinical isolates by using Southern blot hybridization. Clinical isolates (105 fluoroquinolone-resistant and 160 fluoroquinolone-susceptible) were tested for lysogeny by using a PCR assay and functional prophage carriage was studied by mitomycin C induction. Fluoroquinolone-resistant strains harbored fewer inducible prophages (17/43) than fluoroquinolone-susceptible strains (49/70) (P = 0.0018). In addition, isolates of clones associated with fluoroquinolone resistance [CC156 (3/25); CC63 (2/20), and CC81 (1/19)], had lower frequency of functional prophages than isolates of clones with low incidence of fluoroquinolone resistance [CC30 (4/21), CC230 (5/20), CC62 (9/21), and CC180 (21/30)]. Likewise, persistent strains from patients with chronic respiratory diseases subjected to fluoroquinolone treatment had a low frequency of inducible prophages (1/11). Development of ciprofloxacin resistance was tested with two isogenic strains, one lysogenic and the other non-lysogenic: emergence of resistance was only observed in the non-lysogenic strain. These results are compatible with the lysis of lysogenic isolates receiving fluoroquinolones before the development of resistance and explain the inverse relation between presence of inducible prophages and fluoroquinolone-resistance.