Dependence of irradiation temperature in the response of iron salts.

A potential dosimeter based on aqueous frozen solutions and solid-state salt are presented for the evaluation of the energy transferred during the interaction of high-energy radiation with matter at low temperature. The foundation of these dosimeters, both the solid state and the frozen solutions, is based on the measurement of the change of the iron oxidation state. The systems were irradiated with gamma radiation at different doses (up to 10 MGy), and at different temperatures (from 77 to 298 K). The irradiated samples were analysed by UV-spectroscopy and Mössbauer spectroscopy. A theoretical model was developed for the chemical reactions system. This model reproduces the experimental effects produced by the irradiation in aqueous solutions of ferrous salt. The results showed that the response of the dosimeters depends on the irradiation temperature. At low-radiation doses, the response was linear. In particular, this work can be applied to low-temperature dosimetry can be specially applied to simulation experiments of extraterrestrial bodies, as well as in general to space research.

[Surveillance of surgical wound infections. 18-month experience in the Instituto Nacional de Cancerología]. / Vigilancia de las infecciones de herida quirúrgica. Experiencia de 18 meses en el Instituto Nacional de Cancerología.

OBJECTIVE: To calculate the surgical site infection (SSI) rates with a surgical prospective surveillance program and postdischarge follow-up. MATERIAL AND METHODS: During a 18 months period (01/01/93 to 04/30/94), a surgical wound surveillance program followed on the surgeries practiced at the National Institute of Cancerology, a referral center situated in Mexico City. Rates per 100 surgeries were calculated for the surgical services and for each of the wound class strata. The SS's were classified according to the 1992 Center for Disease Control definitions for surgical infections. RESULTS: Three thousand, three hundred and severity-two surgeries were assessed; 313 were diagnosed as infected: 140 (44.7%) were superficial incisional, 137 (43.7%) were deep incisional and 36 (11.5%) were organ and space infections. The SSI rate for this period was 9.28%; for the clean, clean-contaminated, contaminated and dirty surgeries the rates were 7.35, 10.5, 17.3 and 21.5% respectively. The rates for each service were: gastroenterology, 14.13%; breast tumors, 11.08%; mixed tumors, 10.98%; gynecology, 9.06%; urology, 7.38%; head and neck, 7.13%, and thoracic surgery, 1.81%. On average SSI were detected at 11.6 +/- 6.23 days, eighty-five (27.16%) were diagnosed while the patient was in-hospital, the remaining 228 (72.84%) were detected after discharge. In 134 (42.8%) patients a culture was obtained. The bacteria most frequently found were: E. coli, 38 (22.5%); coagulase negative Staphylococci, 23 (13.6%); Pseudomonas sp., 22 (13%); S. aureus, 16 (9.4%); and Enterococcus, 13 (7.7%). CONCLUSIONS: The prospective surveillance program with a follow-up for 30 days increased by 400% the chance to identify a SSI. The SSI rate for clean and clean-contaminated surgeries are above the rates reported in the literature.

Fcgamma receptor-mediated mitogen-activated protein kinase activation in monocytes is independent of Ras.

Receptors for the Fc portion of immunoglobulin molecules (FcR) present on leukocyte cell membranes mediate a large number of cellular responses that are very important in host defense, including phagocytosis, cell cytotoxicity, production and secretion of inflammatory mediators, and modulation of the immune response. Cross-linking of FcR with immune complexes leads, first to activation of protein-tyrosine kinases. The molecular events that follow and that transduce signals from these receptors to the nucleus are still poorly defined. We have investigated the signal transduction pathway from Fc receptors that leads to gene activation and production of cytokines in monocytes. Cross-linking of FcR, on the THP-1 monocytic cell line, by immune complexes resulted in both activation of the transcription factor NF-kappaB and interleukin 1 production. These responses were completely blocked by tyrosine kinase inhibitors. In contrast, expression of dominant negative mutants of Ras and Raf-1, in these cells, did not have any effect on FcR-mediated nuclear factor activation, suggesting that the mitogen-activated protein kinase (MAPK) signaling pathway was not used by these receptors. However, MAPK activation was easily detected by in vitro kinase assays, after FcR cross-linking with immune complexes. Using the specific MAPK/extracellular signal-regulated kinase kinase (MAPK kinase) inhibitor PD98059, we found that MAPK activation is necessary for FcR-dependent activation of the nuclear factor NF-kappaB. These results strongly suggest that the signaling pathway from Fc receptors leading to expression of different genes important to leukocyte biology, initiates with tyrosine kinases and requires MAPK activation; but in contrast to other tyrosine kinase receptors, FcR-mediated MAPK activation does not involve Ras and Raf.

Frequency of intestinal parasites in adult cancer patients in Mexico.

Approximately 28% of the Mexican population has intestinal parasites. Oncologic patients receiving chemotherapy should have a coproparasitoscopic study to avoid disseminated parasitic infections. The frequency of intestinal parasites, including Cryptosporidium and Isospora, was evaluated in 100 diarrheic (DS) and 100 formed stools (FS) from adult patients recently diagnosed with cancer, using wet mounts stained with Kinyoun, saccharose and ZnSO4 procedures stained with Lugol's iodine. Seven patients with DS and three with FS had more than one parasite. Pathogenic intestinal parasites were seen in 26% of DS and 15% of FS. Of the frequent parasites, Entamoeba histolytica was found in 12 DS and in 2 FS (p = 0.01), Giardia lamblia in three DS and six FS and Hymenolepis nana in eight DS and 10 FS. Other pathogenic parasites were found only in DS: Cryptosporidium sp. in five patients, Ascaris lumbricoides in two, Strongyloides stercoralis in two and Isospora sp. in one. Cryptosporidium and Isospora were only identified by wet mounts stained with Kinyoun while other parasites were identified by flotation procedures. Since six (3%) of our patients had coccidia, the laboratory must perform special techniques for their detection. In epidemiologic settings where there is a high prevalence of intestinal parasitic infections the coproparasitoscopic studies should be performed and antiparasitic treatment provided before starting chemotherapy.

Toxoplasmosis of the central nervous system in patients with AIDS in Mexico.

Toxoplasmosis of the central nervous system (CNS) is the most common cause of intracerebral lesions in patients with AIDS. It is now standard clinical practice to treat empirically, based on clinical and radiographic findings, and to perform a biopsy of the lesion only in those patients who fail to have a clinical and radiographic response after two weeks of therapy. This study describes the presentation and response to therapy of central nervous system toxoplasmosis in patients with AIDS at a private practice in Mexico City. A retrospective chart and radiology review of all patients with AIDS treated empirically for toxoplasmosis between 1988 and 1993 was performed. A total of 177 patients with AIDS were seen, nine (5.1%) had toxoplasmosis. Patients with toxoplasmosis were males with a median age of 39 years (range 26 - 65). In two patients, toxoplamosis of the CNS was the initial manifestation of HIV infection, all others had a prior diagnosis of AIDS with a mean of 10 months between their first AIDS defining event and the diagnosis of toxoplasmosis. The median CD4+ T-cell count at the time of the diagnosis of toxoplamsosis was 78 cells/microL. Most patients had headache associated with other focal neurological symptoms such as hemiplegia (2), hemiparesis (2) or seizures (4). Only 4 out of 9 patients had fever as part of their initial clinical presentation. Serum IgG antibodies against Toxoplasma gondii were positive in 6 out of 7 patients tested, while IgM antibodies were negative in all patients. On imaging studies (Computerized Tomography or Magnetic Resonance Imaging), 4 patients had a single lesion while the rest had two or more lesions. Two patients were initially treated with pyrimethamine/sulfadiazine and were later changed to pyrimethamine/clindamycin, which was the treatment given from the beginning to all other patients. One patient died of an intralesional hemorrhage two weeks after the diagnosis despite adequate therapy. The probability of surviving 6 months after the diagnosis of toxoplasmosis was 60%. The findings of these authors are similar to those reported in other series where toxoplasmosis of the CNS is a late complication of HIV infection associated with a CD4+ cell count of < 100 cells/microL. However, survival was short in spite of a good response to therapy.

Chemotherapy-associated oral mucosal lesions in patients with leukaemia or lymphoma.

In order to determine the incidence rate of oral lesions associated with chemotherapy, as well as well as its association with clinical and laboratory parameters and potential risk factors, 50 in-patients with non-Hodgkin's lymphoma or leukaemia under chemotherapy were followed from January 1993 to May 1994. Basal and weekly oral examinations were performed. Clinical and laboratory data were registered. Wilcoxon's rank sum test, chi square test, univariate and multivariate logistic regression analyses were used, 36 individuals with leukaemia and 14 with non-Hodgkin's lymphoma were followed for 158 weeks; mean age was 33 years (range 15-85). Oral lesion incidence rate was 45/100 patients-week. Exfoliative cheilitis and infections (herpes and candidosis) were the most common oral complications, followed by haemorrhagic lesions and mucositis. Haemorrhagic lesions correlated with thrombocytopenia (RR = 30.5). Etoposide administration (RR = 8.6), alkylating agents (RR = 15.6), a prior course of chemotherapy (RR = 23.2) and neutropenia (RR = 4.16) were predictors of mucositis. Oral lesions were a common complication in this study, and a possible association of mucositis with several factors is suggested.

[A surveillance program for surgical wound infections at the National Institute of Cancerology of Mexico]. / Programa de vigilancia de infección de herida quirúrgica en el Instituto Nacional de Cancerología de México.

OBJECTIVES: To evaluate the results of a prospective wound infection surveillance program during its first semester of operation, and to analyse the risk factors associated to wound infection. METHODS AND DESIGN: From January 01 to June 30 1993, 1103 surgeries were prospectively followed. The incidence rates of infection were calculated and a case control analysis was done to evaluate the associated risk factors to POWI (postoperative wound infection). SETTING: An oncological tertiary-care center. RESULTS: The POWI rate was 9.0 per 100 surgeries. By univariate analysis the associated risk factors were: obesity (OR = 2.07 CI95% = 1.19-3.64), one drainage (OR = 2.10 CI = 1.33-3.31), two drainages (OR = 3.14 CI = 1.85-5.26), length of stay of the drainage (patients with wound infection: 15.2 +/- 6.7 days vs. patients without wound infection: 8.2 +/- 6.6 days), duration of operation (patients with wound infection: 188 +/- 163 minutes vs. patients without wound infection: 122 +/- 127 minutes) and duration of preoperative hospitalization (patients with wound infection: 2.9 +/- 6.4 days vs. patients without wound infection 1.5 +/- 3.0 days). The associated risk factors by regression analysis were: obesity (OR = 1.93 CI = 1.08-3.43), two drainages (OR = 2.09 CI = 1.03-4.05) duration of operation > = 120 minutes (OR = 1.96 CI = 1.00-3.86) and duration of preoperative hospitalization (OR = 1.03 CI = 1.00-1.09). CONCLUSIONS: The program showed a previous under-reporting of POWI from 4.2-4.8 per 100 surgeries in the previous seven years to 9.0 in the first semester of operation. It also identified the associated risk factors to POWI in our institution.

[AIDS and neoplasms in Mexico]. / SIDA y neoplasias en México.

OBJECTIVE: To describe the epidemiological profile of AIDS and malignancies in Mexico. MATERIAL AND METHODS: The study population included a group of AIDS patients seen at four National Institutes of Health and one at a general hospital in Mexico City, from 1983 to 1992. Demographic, clinical and laboratory information was obtained. RESULTS: A total of 202 patients were studied; 199 men and three women. The mean age was of 34.5 years (range 18-67 years). Kaposi's sarcoma was the most frequent malignancy, with 166 cases, followed by non-Hodgkin's lymphoma, with 33 cases. The three women had non-Hodgkin's lymphoma, one of them associated with cervical carcinoma. Rectal cancer was present in three cases. DISCUSSION: The spectrum of AIDS-associated malignancies in Mexico is similar to that described in other populations. The early diagnosis of this complication is necessary, as well as the search for therapeutic actions to prevent severe immunosuppression and the consequent appearance of malignancies.

Cancer of the mobile tongue in Mexico. A retrospective study of 170 patients.

Histological reports of 170 patients with cancer of the mobile tongue between 1977 and 1989 were identified at the Instituto Nacional de Cancerología (INCan), in Mexico City. Demographic, clinical and histological information was retrospectively reviewed. Chi-square, Student's t-test and Wilcoxon rank-sum test were applied for comparisons, and Kaplan-Meier curves, log-rank test and Cox proportional hazards for survival analysis. Of the 161 patients with mobile tongue squamous cell carcinoma (MTSCC), 104 (65%) were males and 57 (35%) were females. The mean age was 60 years old (range 19-91). T1 and T2 lesions comprised 35%, T3 and T4 lesions 65%. There was a statistically significant association between size of the tumour and lymph node involvement (P < 0.0001). The proportion of cases with advanced disease was 80% for males and 57% for females (P = 0.008). The 5-year survival rate was 16% (CI 10.2-22.8%). Cancer of the mobile tongue in Mexico still has a poor prognosis. Efforts should be made to reduce the delay in diagnosis of MTSCC, in order to increase the cure rates and improve the quality of life of the patients.

Experience of an intravenous therapy team at the Instituto Nacional de Cancerología (Mexico) with a long-lasting, low-cost silastic venous catheter.

Means of vascular access are fundamental in the management of cancer. However, since current intravenous devices for long-term treatment are expensive and necessitate a high degree of education among medical personnel, in developing countries they are impractical for use in most of the population. We describe the use of a nontunneled, low-cost, long-lasting Silastic catheter (LLSC), cared for by an intravenous therapy team (IVTT), in 462 patients with cancer. The rate of infectious complications was 0.66 infections per 1,000 catheter-days, which is as low as that reported in association with other catheters in developed countries. Neutropenia and skin and/or soft-tissue infections were significant risk factors associated with LLSC-related infections. We believe that use of this catheter may be an alternative for patients with cancer who need chemotherapy, as long as an IVTT is established for its care. Our experience could be useful for practitioners in countries with similar socioeconomic characteristics.

Diagnostic laparotomy in fever of unknown origin.

Twenty five consecutive patients with fever of unknown origin (FUO) who underwent diagnostic laparatomy (DL) are reviewed. There were 14 females and 11 males, with a mean age of 34 years. The main symptoms and signs besides fever were malaise, weight loss, varied abdominal complaints, peripheral lymph nodes enlargement, hepatomegaly and splenomegaly. The main laboratory abnormalities were: anemia, leukocytosis, and mild alterations in liver function tests. CT scan was performed in 14 patients: hepatomegaly, splenomegaly and or retroperitoneal nodes were found in 10 of them. During laparotomy, an extensive exploration of intra-abdominal organs was performed, taking multiple biopsies for histopathologic and microbiologic analysis. Splenectomy was performed in 17 patients, prophylactic appendectomy in four, and cholecistectomy in one. Laparotomy was useful to establish a diagnosis in 64 percent of cases. The most frequently diagnosed pathologies were lymphoma and tuberculosis. Postoperative morbidity was 12% and mortality was 4%. Mean follow-up was 29 months. When preoperative data were analyzed, no predictive factors were found for a laparotomy with diagnostic success. It is concluded that DL is a useful last-step procedure in the diagnostic work-up for patients with FUO.