Improvements in the radiochemical method for separating 226Ra in solid samples through coprecipitation with BaSO4.

The aim of this work was to improve the commonly used method for 226Ra determination in water and to establish its application in solid samples. This method is based on the coprecipitation of Ra with BaSO4 and gross alpha counting of the precipitate. An exhaustive study of the coprecipitation behaviour of the most abundant cations present in solid samples was performed to avoid incorrect radiochemical yields. As a result, it was considered necessary to introduce two new purification steps into the conventional method. Likewise, two nuclides, 241Am and 226Ra, were compared to obtain the mass efficiency curve given their different behaviour in the coprecipitation process. While Ra behaves similarly to Ba, Am coprecipitates, forming mixed crystals that may behave differently in the self-absorption process. The influence of the cations on the chemical yield with no precipitate purification was: Sr2+≫Fe3+>Mg2+≈Ca2+>K+≈Na+. The method was successfully applied to soil, sediment, and plant ash samples.

Higher prevalence of meticillin-resistant Staphylococcus aureus among dental students.

In order to test the hypothesis that more dental students are meticillin-resistant Staphylococcus aureus (MRSA) carriers than non-dental students, 100 dental students with five to six years of exposure to patients and 81 non-dental students were tested for nasal and pharyngeal MRSA carriage by polymerase chain reaction. All 181 students were clinically healthy and none had taken antibiotics. Significantly more dental students (20/100) carried MRSA than non-dental students (5/81) (odds ratio: 4.04; 95% confidence interval: 1.6-12.6; P = 0.0033). Also, more dental students' mobile phones (8/100) carried MRSA. All MRSA isolates were distinguished by pulsed-field gel electrophoresis from epidemiologically significant strains. The results suggest that dental students are occupationally exposed to MRSA.

Dental school deans' and dentists' perceptions of infection control and HIV/AIDS patient care: a challenge for dental education in Mexico.

HIV/AIDS patients face unique oral diagnostic and treatment challenges. The aim of this investigation among dental school deans (DSD) and graduate school applicants (GSA) who had qualified from 30 different dental schools was to assess their perceptions on dental education relevant to infection control (IC) and HIV/AIDS patient care. The questionnaire included Likert-type scale evaluations of agreement with statements. Of 158 questionnaires, 23 DSD (68% response rate), and 123 GSA (100% response rate) returned valid questionnaires. Fifteen (65%) DSD and 89 (72%) GSA ranked as "very strong" their perception that infection control prevents the transmission of blood borne viruses. However, the perception prevailed, among DSD and GSA, that HIV infection was a "very strong" to "strong" occupational hazard. Special reprocessing of instruments used on HIV patients was frequently reported. Many considered "very strong" to "strong" that HIV/AIDS patients must be treated in specialized clinics, and nearly half (48%) of the DSD and one third (35%) of the GSA stated that their school does refer HIV/AIDS patients to dental treatment in specialized clinics. These results indicate that many dental schools in Mexico must provide better education on IC and HIV/AIDS patient care to enhance attitudes toward HIV/AIDS patients.

Mexican dental school deans' opinions and practices regarding oral cancer, 2007.

Dentists must be trained in oral cancer (OC) screening and counseling. However, educational gaps exist in OC prevention worldwide. The objective of this investigation was to assess self-reported perceptions and practices relevant to OC education among Mexican dental school deans. At a leadership meeting in 2007, deans were given a questionnaire containing Likert-type scale evaluations of agreement with statements. Associations between variables were analyzed with Pearson's chi-square test. Of thirty-four deans attending, twenty-three (68 percent response rate) answered the questionnaire in full. Among the respondents, 83 percent believed "very strongly" that dentists must look for OC, but only 52 percent believed "very strongly" that OC screening must be adopted as a standard practice. Fifty-two percent ranked dentists' responsibility in looking after their patients' overall health as "very strong." The deans indicated less support for dentists' roles to intervene in tobacco and alcohol cessation. Participant deans lead institutions that provide education for over 12,000 dental students; their low awareness on OC screening and counseling may hinder the establishment of routine standardized screening and health promotion that help save human lives.

Cigarette smoking and dental caries among professional truck drivers in Mexico.

BACKGROUND: Professional truck drivers are at high risk of chronic diseases. Further examination of tobacco use and its impact on oral health is warranted - both in terms of the direct association between tobacco use and poor oral health, and in terms of tobacco use being an indicator of poor health behaviors. OBJECTIVE: To estimate the possible association between smoking and dental caries experience in a population with high tobacco use. METHODS: Drivers' licenses are periodically re-issued by the Mexican government and as part of the licensing process a physical exam takes place. We administered a free, standardized questionnaire together with an oral examination (WHO criteria) included in the physical exam, targeting a random sample of applicants in Mexico City. RESULTS: A total of 824 dentate males (mean age 35.5 +/- 10 years) took part in the study, of whom 49.2% were current smokers and 23.2% were former smokers. Caries experience was mean DMFT 8.95 (+/- 6.05). Only 18.0% of participants had 'excellent' or 'good' oral hygiene. The prevalence of 'large' cavities increased as the number of cigarettes/day increased from 14.6% (1-3 cigarettes/day) to 33.3% (> or =10 cigarettes/day). Using multiple linear regressions, we found that older age, poorer oral hygiene, higher education, and greater tobacco exposure were significantly associated with higher caries experience (DMFT). An interaction was observed with oral hygiene and tobacco: drivers that smoked and had 'poor' oral hygiene showed the highest number of large cavities and missing teeth. Health promotion interventions are needed in this at-risk population group.

Synergy of adoptive T-cell therapy and intratumoral suicide gene therapy is mediated by host NK cells.

In situ tumor cell killing by the herpes simplex virus thymidine kinase (HSVtk) gene can effectively prime antitumor T-cell responses, at least in part through local induction of a pro-inflammatory environment. Therefore, we reasoned that tumor-associated HSVtk expression would significantly enhance the efficacy of adoptive T-cell transfer (ACT) of (tumor) antigen-specific T cells into tumor-bearing hosts. When B16ovaHSVtk tumors were treated with ganciclovir (GCV), along with suboptimal numbers of activated OT-1T cells, complete tumor regressions were observed where GCV, or ACT, alone was completely ineffective. To our surprise, analysis of regressing tumors showed no increases in intratumoral OT-1T cell trafficking. However, the intratumoral percentages of both OT-1 and endogenous natural killer (NK) cells were substantially increased over controls. Depletion of endogenous NK cells abrogated the efficacy of the combination therapy and reduced the percentages of interferon-gamma(IFNgamma)-secreting OT-1T cells in mice that received combined therapy to levels similar to those of control mice. These data suggest that even relatively low levels of gene transfer of suicide genes into tumors may have therapeutic value as an adjuvant for other T-cell therapies, by providing immunological signals that support T-cell activation and expansion in vivo.

VSV-G pseudotyped, MuLV-based, semi-replication-competent retrovirus for cancer treatment.

Low levels of gene delivery in vivo using replication-defective retroviral vectors have severely limited their application for clinical protocols. To overcome this problem, we describe here a semi-replication-competent retrovirus (s-RCR) in which the gag-pol and envelope (VSV-G, vesicular stomatitis virus G protein) genes were split into two vectors. This system offers potential advantages over both replication-defective vectors, in terms of efficiency of in vivo spread through a tumor, and all-in-one replication-competent vectors in terms of the payload of therapeutic genes that can be carried. We achieved a viral titer of s-RCR viruses approximately 70-fold higher than VSV-G pseudotyped, replication-defective vectors. In addition, s-RCR vectors induced tumor killing by the cytotoxicity of VSV-G during viral spread. Inclusion of the herpes simplex virus thymidine kinase (HSVtk30) gene into vectors significantly improved tumor killing activity followed by ganciclovir (GCV) treatment in vitro under conditions of low-level viral replication. However, at high levels of viral spread, VSV-G-mediated cytotoxicity predominated. Xenografts of human fibrosarcoma HT1080 cells, preinfected by semi-replicative green fluorescent protein vectors (semi-GFP), were completely non-tumorigenic in nude mice. Implantation of cells preinfected by semi-replicative TK30 vectors (semi-TK30) mixed with parental HT1080 cells at a ratio of 1:1 efficiently prevented tumor growth in mice treated by GCV. Direct intratumoral injection of HT1080 tumors growing in nude mice, or B16 murine melanoma in immunocompetent mice, with semi-TK30 viruses significantly prolonged survival. Injection of autologous cells (B16) producing semi-TK30 vector into B16 tumors prolonged survival only in mice treated with GCV but not with phosphate-buffered saline (PBS). In contrast, when xenogeneic cells (293T) producing semi-TK30 vectors were injected into B16 tumors, an optimal survival advantage was obtained in mice treated with PBS rather than GCV. These data indicate that complex interactions exist between direct cytotoxicity of VSV-G and HSVtk expression when placed in the context of additional immune parameters, which combine to determine the efficacy of the therapy. Taken together, our data suggest that s-RCR vectors have some potential advantages for development to deliver genes into tumors for cancer treatment but that a combination of factors will impact on the decision as to whether the s-RCR strategy is worth developing to full clinical trials.

[Middle latency auditory evoked potentials in critical care children: preliminary study]. / Potenciales evocados auditivos de latencia media en el niño críticamente enfermo: estudio preliminar.

BACKGROUND: Middle latency auditory evoked potentials (MLAEP) reflect changes in electroencephalogram waves after an auditory signal and represent the earliest cortical response to acoustic stimulus. They are therefore used to measure variations in the level of consciousness. MLEAP have been used to measure the depth of anesthesia during surgical procedures, but experience in critical care patients is very limited. OBJECTIVE: To analyze the utility of MLAEP for monitoring the level of sedation in critically ill children. METHODS: Level of consciousness was monitored through MLAEP by placing special headphones and three sensors situated in the frontal and preauricular regions. Simultaneously, the level of sedation was measured using the COMFORT scale and the Bispectral Index (BIS) in distinct clinical situations. RESULTS: We studied six critically ill children in whom MLAEP helped us to evaluate the level of consciousness: light sedation, natural sleep, deep sedation, sedation in a paralyzed child, and brain death. MLAEP showed a good correlation with the COMFORT scale and BIS in light and deep sedation and were effective in the early detection of brain death in one patient. In the paralyzed patient, MLAEP was able to detect undersedation. In one patient, a pacemaker interfered with the MLAEP signal. CONCLUSIONS: MLAEP can be useful in evaluating the level of consciousness and sedation in critically ill children. Further studies with larger samples are required to analyze the limitations and reproducibility of this type of monitoring in children of different ages.

The perforin-dependent immunological synapse allows T-cell activation-dependent tumor targeting by MLV vector particles.

We have reported that retroviral particles adhered to the surface of antigen-specific T cells can be carried to metastases following adoptive transfer in vivo, a process we have called viral hitch hiking. Following antigen-driven T-cell accumulation at tumors, viral particles productively infect tumor cells via envelope/receptor dependent interactions ('hand on' of virus from the T cell to the tumor cell). We describe here a second envelope/receptor independent pathway of viral hand on from T cells, dependent on T-cell activation. We show that the endosomolytic property of perforin promotes release of viral particles from endosomes into which they are co-delivered along with cytotoxic granules from the activated T cell. Therefore, hand on of MLV particles lacking any envelope can be used for in vivo delivery of vectors, where targeting is at the extremely specific level of recognition of antigen by the T-cell receptor, thereby dispensing with the need to engineer viral envelopes. These data reveal a novel pathway by which MLV viral particles exploit a functional immunological synapse and present new opportunities both to improve the efficacy of adoptive T-cell transfer and to target vectors for systemic gene delivery.

Induction of cell stress through gene transfer of an engineered heat shock transcription factor enhances tumor immunogenicity.

Heat shock protein expression and release is closely associated with immunogenic forms of cell death. We show that activation of the stress response within tumor cells during cell death, using an engineered form of the heat shock transcription factor, leads to an immunogenic death. Cells dying through 'stressful death' show decreased phagocytosis by macrophages in vitro. Moreover, cells expressing heat shock proteins during cell death are significantly more protective against subsequent tumor challenge. These data demonstrate the utility of activating cellular stress programs over the course of cytotoxic therapies to enhance immune responses to dying cells.

Caries risk assessment from dental plaque and salivary Streptococcus mutans counts on two culture media.

This study attempted to determine which combination of plaque or saliva, and tryptic soy agar, bacitracin (TSY20B) or mitis salivarius, bacitracin media, yielded the highest caries-predictive values for mutans counts in children with different caries prevalence. Sixty children were divided into three equally sized groups: caries free, low caries and high caries. Eighteen months later, their caries incidence and initial mutans count were compared. Fissure plaque on TSY20B yielded a high correlation between mutans counts and caries prevalence (P<0.009, r=3346) and incidence (P<0.003, r=4521). The caries-predictive values obtained demonstrate that the coefficient of variation of mutans counts from lower first-molar fissure plaque on TSY20B accounts for 20.4% of the variation in final caries index. This strong correlation provides a valuable tool for the identification of caries-prone individuals.

[The evidence for higher blood pressures in children and adolescents of the rural interior of Galicia than in other locations in Spain]. / Evidencia de presiones arteriales más elevadas en niños y adolescentes del interior rural de Galicia que en otras localizaciones en España.

AIM: To analyze differences in blood pressure levels in children and adolescents in Galicia with those of peers living in other parts of Spain. DESIGN: Cross-sectional study done in a rural area in Galicia. PARTICIPANTS: 870 boys and girls 6 to 16 years old. They are compared with published data from the RICARDIN study, that includes 10,042 participants selected at the schools in nine centers of Spain (one was the center in Galicia). MEASUREMENTS: Standardized methodology and certification procedures were used in Galicia and Spain to measure weight, height, Quételet index, systolic (SBP) and fifth-phase diastolic blood pressure (DBP5) and sexual maturation. Data are presented by sex and age group (1 year) both in Galicia and Spain. RESULTS: From 11 years and above, girls in Galicia present higher SBP than in Spain. In boys, the difference appears later. Galicia shows higher DBP5 levels than Spain in every age-sex group. In relation to obesity, the differences are of a small magnitude in the Quételet index, again, higher values in Galicia. CONCLUSIONS: This is the first population-based study available that rules out the possibility that the observed differences, previously already suggested, could be attributed to methodological problems. The differences in blood pressure and obesity between Galicia and other areas of Spain, already previously suggested in adults, can be the reflection of differences present from childhood.

[Fluoride content of table salt in Mexico City]. / Flúor contenido en la sal para consumo humano distribuida en la ciudad de México.

The fluoride content of a sample of bags of salt for sale in Mexico City was measured in order to estimate the proportion of marketed salt that contained the quantity of fluoride set by the National Program for Prevention of Dental Caries through Consumption of Fluoridated Table Salt. The effectiveness of that program had never been evaluated. In March 1993, bags of salt were obtained from 70 of the 3544 neighborhoods that make up Mexico City. The stores were selected by simple random sampling. Salt was likewise purchased from 20% of the 146 supermarkets and self-service stores in the city, also selected as a random sample. Then, blind measurement was done of the fluoride content of 221 bags of salt. The true content of this element was often found to be below the amount called for by the government. In addition, it did not coincide with the quantity indicated on the package label, which is a violation of the law.

[World changes in the occurrence of dental caries]. / Fluctuaciones mundiales en la frecuencia de caries dental.

Aiming to draw the current world outlook of the caries-forming process, pertinent information was compiled from the World Health Organization and various other sources. Data from the different countries were grouped in five categories, depending on the average number of teeth affected. On the basis of compiled data and the experience of countries enjoying the highest levels of buccal health, a set of tactics are proposed toward diminishing the incidence of cavities in our country.

[Meningitis caused by Candida in a premature infant]. / Meningitis por Candida en un prematuro.

A case of Candida meningitis in a premature infant treated with amphotericin B IV for 41 days, resulted in negative CSF cultures after 5 days of therapy. Amphotericin B was also given intraventricularly for 21 days; purulent meningitis was a complication from this kind of therapy. Psychometric evaluation showed a mental age of 3 months in a chronological age of 7 months. Only one premature infant has been reported in the literature with intraventricular amphotericin B treatment. A review of Candida meningitis diagnosed before death in infants less than 1 year of age and a discussion of the modern therapy is presented.