The anticancer activity of bovine lactoferrin is reduced by deglycosylation and it follows a different pathway in cervix and colon cancer cells.

Bovine lactoferrin (bLF) is a glycosylated protein with purported beneficial properties. The aim of this work was to determine the role of bLF glycosylation in the adhesion, internalization, and growth inhibition of cancer cells. The viability of cervix (HeLa) and colon (Caco-2) cancer cells (MTT assay and epifluorescence microscopy) was inhibited by bLF, while deglycosylated bLF (bLFdeg) had no effect. Adhesion to cell surfaces was quantified by immunofluorescence assay and showed that bLF was able to bind more efficiently to both cell lines than bLFdeg. Microscopic observations indicated that bLF glycosylation favored bLF binding to epithelial cells and that it was endocytosed through caveolin-1-mediated internalization. In addition, the mechanism of action of bLF on cancer cell proliferation was investigated by determining the amount of phosphorylated intermediates of signaling pathways such as epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and protein kinase B (known as Akt). Chemoluminescence immunoassay of phosphorylated intermediates showed that bLF inhibited Akt phosphorylation, consistent with its growth inhibiting activity. This assay also indicated that the bLF receptor/signaling pathways may be different in the two cell lines, Caco-2 and HeLa. This work confirmed the effect of glycosylated bLF in inhibiting cancer cell growth and that glycosylation is required for optimal surface adhesion, internalization, and inhibition of the ERK/Akt pathway of cell proliferation through glycosylated cell surface receptors.

Maxillary mucormycosis and aspergillosis in post-COVID-19 patients in Mexico: A case series.

BACKGROUND: Fungal infections, during or as a consequence of SARS-CoV-2 infection, associated with uncontrolled diabetes mellitus and indiscriminate use of corticosteroids have been reported. In the jaw, mostly mucormycosis has been diagnosed in hospitals. METHODS: A retrospective, cross-sectional, descriptive study of the clinical, imaging, and histopathologic characteristics of maxillary invasive fungal infection in post-COVID-19 patients diagnosed in a private non-hospital oral pathology service in Mexico during 2020-2022 was conducted. RESULTS: We found 20 cases of maxillary invasive fungal infections in post-COVID-19 patients, 75% including a diagnosis of mucormycosis and 25% diagnosed as probable aspergillosis. The most common signs and symptoms were exposed necrotic bone followed by tooth mobility, discharge, and pain. On imaging, unilateral maxillary sinus involvement was observed in 6 cases (30%), and bilateral maxillary sinus involvement was observed in 3 cases (15%). CONCLUSIONS: It is essential to consider the association of osteonecrosis of the jaw in post-COVID-19 patients, with aspergillosis, not only mucormycosis, for early diagnosis and appropriate treatment.

Unusual Manifestation of Membranous Dysmenorrhea: Case Report.

BACKGROUND In the 18th century, Morgagni described membranous dysmenorrhea as the sudden and complete detachment of the decidua during menstruation. This causes intense and painful contractions of the myometrium, aggravated by the expulsion of tissues produced by the decidualization of the endometrium. It is a rare pathology associated with oral contraceptives, ectopic pregnancies, abortions, and natural cycles, with consequent thickening and endometrial decidualization with molding of the tissue of the uterine cavity of membranous appearance. The definitive diagnosis is made by histopathological examination. CASE REPORT A 43-year-old female patient came for urgent consultation for an acute picture of severe pain in the lower abdomen, radiating to the genital area with transvaginal bleeding of 2 h of evolution. She had no significant past medical history. A transvaginal ultrasound was performed and showed an unchanged endometrial cavity. A vaginal examination revealed a foreign body of soft consistency; therefore, a speculum examination was performed, which showed tissue of endometrial origin located in the cervical canal of a reddish spongy texture. The tissue was removed, thus improving the symptomatology, and was sent to the pathological anatomy service for histopathologic diagnosis. CONCLUSIONS Membranous dysmenorrhea is a rare gynecologic disorder with only a few documented cases. According to other case reports, our patient's case, at age 43 years, was an atypical presentation. The clinical features and association with this pathology allowed the diagnosis and its confirmation by histopathological examination.

Stem-Loop Structures in Iron-Regulated mRNAs of Giardia duodenalis.

Giardia duodenalis is a significant cause of waterborne and foodborne infections, day-care center outbreaks, and traveler's diarrhea worldwide. In protozoa such as Trichomonas vaginalis and Entamoeba histolytica, iron affects the growth, pathogenicity mechanisms, and expression of virulence genes. One of the proposed iron regulatory mechanisms is at the post-transcriptional level through an IRE/IRP-like (iron responsive element/iron regulatory protein) system. Recently, the expression of many putative giardial virulence factors in the free-iron levels has been reported in subsequent RNAseq experiments; however, the iron regulatory mechanism remains unknown. Thus, this work aimed to determine the effects of iron on the growth, gene expression, and presence of IRE-like structures in G. duodenalis. First, the parasite's growth kinetics at different iron concentrations were studied, and the cell viability was determined. It was observed that the parasite can adapt to an iron range from 7.7 to 500 µM; however, in conditions without iron, it is unable to survive in the culture medium. Additionally, the iron modulation of three genes was determined by RT-PCR assays. The results suggested that Actin, glucosamine-6-phosphate deaminase, and cytochrome b5 mRNA were down-regulated by iron. To investigate the presence of IRE-like structures, in silico analyses were performed for different mRNAs from the Giardia genome database. The Zuker mfold v2.4 web server and theoretical analysis were used to predict the secondary structures of the 91 mRNAs analyzed. Interestingly, the iron-induced downregulation of the genes analyzed corresponds to the location of the stem-loop structures found in their UTR regions. In conclusion, iron modulates the growth and expression of specific genes, likely due to the presence of IRE-like structures in G. duodenalis mRNAs.

Antitumor activity of bovine lactoferrin and its derived peptides against HepG2 liver cancer cells and Jurkat leukemia cells.

Liver cancer and leukemia are the fourth and first causes, respectively, of cancer death in children and adults worldwide. Moreover, cancer treatments, although beneficial, remain expensive, invasive, toxic, and affect the patient's quality of life. Therefore, new anticancer agents are needed to improve existing agents. Because bovine lactoferrin (bLF) and its derived peptides have antitumor properties, we investigated the anticancer effect of bLF and LF peptides (LFcin17-30, LFampin265-284 and LFchimera) on liver cancer HepG2 cells and leukemia Jurkat cells. HepG2 and Jurkat cells were incubated with bLF and LF peptides. Cell proliferation was quantified by an MTT assay, and cell morphology and damage were visualized by light microscopy or by phalloidin-TRITC/DAPI staining. The discrimination between apoptosis/necrosis was performed by staining with Annexin V-Alexa Fluor 488 and propidium iodide, and the expression of genes related to apoptosis was analyzed in Jurkat cells. Finally, the synergistic interaction of bLF and LF peptides with cisplatin or etoposide was assessed by an MTT assay and the combination index. The present study demonstrated that bLF and LF peptides inhibited the viability of HepG2 and Jurkat cells, inducing damage to the cell monolayer of HepG2 cells and morphological changes in both cell lines. bLF, LFcin17-30, and LFampin265-284 triggered apoptosis in both cell lines, whereas LFchimera induced necrosis. These results suggested that bLF and LF peptides activate apoptosis by increasing the expression of genes of the intrinsic pathway. Additionally, bLF and LF peptides synergistically interacted with cisplatin and etoposide. In conclusion, bLF and LF peptides display anticancer activity against liver cancer and leukemia cells, representing an alternative or improvement in cancer treatment.

Epidemiological and clinical characteristics of pregnant women and neonates with COVID-19 in Northwest Mexico.

INTRODUCTION: The SARS-CoV-2 virus, which causes COVID-19, has spread quickly worldwide, causing millions of cases and thousands of deaths. Some risk factors in the general population are related to the development of severe COVID-19 or death, but in pregnant women and neonates, the information is limited. OBJECTIVE: To determine the epidemiological and clinical characteristics of pregnant women and neonates diagnosed with COVID-19 by RT-PCR and serological tests, and analyze the relationship between the influenza vaccination and COVID-19 symptoms in infected pregnant women in Sinaloa state. METHODS: We collected samples from 116 pregnant women and 84 neonates from the Women´s Hospital of Sinaloa. They were diagnosed with COVID-19 by RT-PCR and serological tests (IgG), and sociodemographic, clinical and laboratory parameters were recorded. RESULTS: A total of 11.2% (13/116) of the pregnant women were RT-PCR+, 25% (29/116) were IgG+ and 4.3% (5/116) were positive for both tests. Symptoms such as rhinorrhea (P = .04), cough (P = .02) and polypnea (P = .04) in pregnant women were related to COVID-19, also leukocyte index was higher in pregnant women with COVID-19 (P = .03), but the associations were lost after the Bonferroni correction. No laboratory parameters or underlying diseases were associated with COVID-19, and most infected pregnant women had mild cases. We found an association between the influenza vaccine and less common COVID-19 symptoms in pregnant women who were infected (P = .01). A total of 7.2% (6/84) of neonates were RT-PCR+, 35.7% (30/84) were IgG+, and there were no symptoms or underlying diseases associated with neonates who were infected. In conclusion, this work demonstrated that some symptoms were related to COVID-19, most pregnant women and neonates had mild cases, and the influenza vaccine could decrease the severity of COVID-19 cases in pregnant women.

Lactoferrin: A Nutraceutical with Activity against Colorectal Cancer.

Homeostasis in the human body results from the tight regulation of several events, since too little inflammation disrupts the process of tissue repair and remodeling, whereas too much exerts a collateral effect by causing tissue damage with life-threatening consequences. In some clinical conditions, such as inflammatory bowel disease (IBD), inflammation functions as a double-edged sword by either enabling or inhibiting cancer development and progression. Generally, cancer develops through evasion mechanisms that regulate cell growth, causing a high rate of uncontrolled proliferation, and mechanisms for evading cell death, such as apoptosis. Moreover, chronic inflammation is a factor that contributes to colorectal cancer (CRC), as observed in individuals with IBD; all these conditions favor an increased rate of angiogenesis and eventual metastasis. Lactoferrin (Lf) is a mammalian iron-binding multifunctional glycoprotein regarded as a natural compound that up- and downregulates both humoral and cellular components of immunity involved in regulating the inflammatory response and maintaining gut homeostasis. Human and bovine Lf share high sequence homology and have very similar antimicrobial, anti-inflammatory, and immunomodulatory activities. Bovine Lf from milk is considered a safe molecule and is commercially available in large quantities. This review mainly focuses on the regulatory effects of orally administered bovine Lf on the inflammatory response associated with CRC; this approach indicates that CRC is one of the most frequently diagnosed cancers and affects the intestinal tract with high clinical and epidemiologic relevance. Thus, this review may provide foundations for the potential use of bovine Lf alone or as a natural adjunct agent to increase the effectiveness and reduce the side effects of anticancer chemotherapy.

Prevalence of Cyclomodulin-Positive E. coli and Klebsiella spp. Strains in Mexican Patients with Colon Diseases and Antimicrobial Resistance.

Colon diseases, such as colorectal cancer (CRC), are multifactor diseases that affect more than one million people per year; recently, the microbiota has been associated with an etiologic factor, specifically bacterial cyclomodulin positivity (CM+). Unfortunately, there are no studies from Mexico that detail the presence of bacterial CM+ in patients with colon diseases. We therefore performed a comprehensive study to investigate the associations and prevalence of cyclomodulin-positive Diarrheagenic E. coli (DEC), non-DEC, and Klebsiella spp. strains isolated from Mexican subjects with colon diseases. In this work, we analyzed 43 biopsies, 87 different bacteria were isolated, and E. coli was the most frequently noted, followed by Klebsiella spp., and Enterococcus spp. E. coli, non-DEC, and EPEC belonging to phylogroup B2 were the most prevalent. More than 80% of E. coli and Klebsiella were CM+. pks, cdt, cnf, and cif were identified. cdt was associated with non-DEC, cif and its combinations with EPEC, as well as cdt and psk with Klebsiella. Lastly, all the CM+ bacteria were resistant to at least one antibiotic (34% were MDR, and 48% XDR). In conclusion, the high prevalence of bacterial CM+ in colon disease patients suggests that these bacteria play an important role in the genesis of these diseases.

Bovine lactoferrin and lactoferrin peptides affect endometrial and cervical cancer cell lines.

Cervical, uterine, and ovarian cancers are the most common malignancies of the female genital tract worldwide. Despite advances in prevention, early diagnosis, effective screening, and treatment programs, mortality remains high. Consequently, it is important to search for new treatments. The activity of bovine lactoferrin (bLF) and LF peptides against several types of cancer has been studied; however, only a few studies report the effect of bLF and LF peptides against cervical and endometrial cancers. In this study, we explored the effect of bLF as well as LF chimera and its constituent peptides LFcin17-30 and LFampin265-284 on the viability of cervical (HeLa, SiHa) and endometrial (KLE, HEC-1A) cancer cell lines. Cell proliferation was quantified with an MTT assay, cell morphological changes and damage were determined by Giemsa and phalloidin-TRITC and DAPI staining, and apoptotic and necrotic cells were identified by Alexa Fluor® 488 Annexin V and propidium iodide staining. Additionally, the effect of combinations of bLF and LF peptides with cisplatin was assessed. bLF and LF peptides inhibited the proliferation of uterine cancer cells and caused cellular morphological changes and damage to cell monolayers. bLF induced apoptosis, LFcin17-30 and LFampin265-284 induced apoptosis and necrosis, and LF chimera induced necrosis. Additionally, bLF and LF chimera showed an additive interaction with cisplatin against uterine cancer cells.

Intestinal amoebiasis: 160 years of its first detection and still remains as a health problem in developing countries.

Amoebiasis is a parasitic disease caused by Entamoeba histolytica (E. histolytica), an extracellular enteric protozoan. This infection mainly affects people from developing countries with limited hygiene conditions, where it is endemic. Infective cysts are transmitted by the fecal-oral route, excysting in the terminal ileum and producing invasive trophozoites (amoebae). E. histolytica mainly lives in the large intestine without causing symptoms; however, possibly as a result of so far unknown signals, the amoebae invade the mucosa and epithelium causing intestinal amoebiasis. E. histolytica possesses different mechanisms of pathogenicity for the adherence to the intestinal epithelium and for degrading extracellular matrix proteins, producing tissue lesions that progress to abscesses and a host acute inflammatory response. Much information has been obtained regarding the virulence factors, metabolism, mechanisms of pathogenicity, and the host immune response against this parasite; in addition, alternative treatments to metronidazole are continually emerging. An accesible and low-cost diagnostic method that can distinguish E. histolytica from the most nonpathogenic amoebae and an effective vaccine are necessary for protecting against amoebiasis. However, research about the disease and its prevention has been a challenge due to the relationship between E. histolytica and the host during the distinct stages of the disease is multifaceted. In this review, we analyze the interaction between the parasite, the human host, and the colon microbiota or pathogenic microorganisms, which together give rise to intestinal amoebiasis.

Synthetic bovine lactoferrin peptide Lfampin kills Entamoeba histolytica trophozoites by necrosis and resolves amoebic intracecal infection in mice.

Amoebiasis caused by the protozoan parasite Entamoeba histolytica remains a public health problem in developing countries, making the identification of new anti-amoebic compounds a continuing priority. Previously, we have shown that lactoferrin (Lf) and several Lf-derived peptides exhibit in vitro anti-amoebic activity independently of their iron-binding activity. Here, we evaluated the amoebicidal effect of synthetic Lf-derived peptides Lfcin-B, Lfcin 17-30, and Lfampin, analyzed the mechanism of death induced by the peptides and determined their therapeutic effects on murine intestinal amoebiasis. MTT assays in trophozoite cultures of E. histolytica exposed to each peptide (1-1000 µM) showed that Lfampin is far more amoebicidal than Lfcins. Lfampin killed 80% of trophozoites at doses higher than 100 µM in 24 h, and FACs analysis using Annexin V/propidium iodide showed that death occurred mainly by necrosis. In contrast, Lfcin-B and Lfcin 17-30 appeared to have no significant effect on amoebic viability. FACs and confocal microscopy analysis using FITC-labeled peptides showed that all three peptides are internalized by the amoeba mainly using receptor (PI3K signaling) and actin-dependent pathways but independent of clathrin. Docking studies identified cholesterol in the amoeba's plasma membrane as a possible target of Lfampin. Oral treatment of intracecally infected mice with the abovementioned peptides at 10 mg/kg for 4 days showed that Lfampin resolved 100% of the cases of intestinal amoebiasis, whereas Lfcin 17-30 and Lfcin-B were effective in resolving infection in 80 and 70% of cases, respectively. These data show that although synthetic bovine Lf-derived peptides exhibit varying amoebicidal potentials in vitro, they do resolve murine intestinal amoebiasis efficiently, suggesting that they may be useful as a therapeutic treatment.

[Unilateral congenital pulmonary lymphangiectasia in a preterm infant]. / Linfangiectasia pulmonar congénita unilateral en un neonato prematuro.

Unilateral congenital pulmonary lymphangiectasia (CPL) is an extremely rare disease of the pulmo nary lymphatic vessels. OBJECTIVE: to present a case of CPL in a premature newborn. CLINICAL CASE: premature male newborn with severe respiratory failure at 2 hours of extrauterine life was treated with exogenous surfactant, catecholamines and high frequency oscillatory ventilation (HFOV). Chest computed tomography (CT) scan showed bullae and air trapping of the left lung; the histopathological study showed cystic dilation of the bronchoalveolar lymphatic channels. The diagnosis of secondary unilateral CPL was made. The clinical course up to 19 months of age was normal and the chest CT scan showed few emphysematous bullae. CONCLUSIONS: CPL must be one of the differential diagnoses in neonates with unexplained respiratory distress. The prognosis will depend on the type of CPL and lung involvement.

Iron-modulated virulence factors of Entamoeba histolytica.

Entamoeba histolytica is a human parasite that causes amoebiasis, a disease that affects the colon and liver and is prevalent worldwide. This protozoan requires a high concentration of iron to survive and reproduce. Iron modulates the expression of parasite virulence factors, including hemoglobinases, hemoglobin-binding proteins and cysteine proteases, as well as proteins related to the amoebic cytoskeleton. This review summarizes the virulence factors that are affected by iron, resulting in upregulation or downregulation of E. histolytica genes. This review also discusses the functionality of iron in the mechanisms of pathogenesis.

Linfangiectasia pulmonar congénita unilateral en un neonato prematuro / Unilateral congenital pulmonary lymphangiectasia in a preterm infant

La linfangiectasia pulmonar congénita (LPC) unilateral es una enfermedad extremadamente rara de los vasos linfáticos pulmonares. OBJETIVO: presentar un caso de LPC en un recién nacido prematuro. CASO CLÍNICO: recién nacido masculino, prematuro, con insuficiencia respiratoria severa a las 2 horas de vida extrauterina, recibió tratamiento con surfactante exógeno, catecolaminas y ventilación de alta frecuencia oscilatoria (VAFO). La tomografía axial computarizada (TAC) de tórax reveló bulas y atrapamiento de aire de pulmón izquierdo, el estudio histopatológico describió dilatación quística de los canales linfáticos broncoalveolares. Se diagnosticó LPC unilateral secundaria. La evolución clínica hasta los 19 meses de edad fue normal y la TAC de tórax mostró escasas bulas enfisematosas. CONCLUSIONES: La LPC debe ser uno de los diagnósticos diferenciales en neonatos con dificultad respiratoria inexplicable. El pronóstico dependerá del tipo de LPC y de la afectación pulmonar.

Unilateral congenital pulmonary lymphangiectasia (CPL) is an extremely rare disease of the pulmo nary lymphatic vessels. OBJECTIVE: to present a case of CPL in a premature newborn. CLINICAL CASE: premature male newborn with severe respiratory failure at 2 hours of extrauterine life was treated with exogenous surfactant, catecholamines and high frequency oscillatory ventilation (HFOV). Chest computed tomography (CT) scan showed bullae and air trapping of the left lung; the histopathological study showed cystic dilation of the bronchoalveolar lymphatic channels. The diagnosis of secondary unilateral CPL was made. The clinical course up to 19 months of age was normal and the chest CT scan showed few emphysematous bullae. CONCLUSIONS: CPL must be one of the differential diagnoses in neonates with unexplained respiratory distress. The prognosis will depend on the type of CPL and lung involvement.

Balance de líquidos y lesión renal aguda en el choque séptico / Fluid balance and acute kidney injury in septic shock

Resumen: Introducción: En el paciente con choque séptico, la administración excesiva de líquidos puede incrementar la morbilidad y mortalidad. El objetivo de este estudio fue evaluar la asociación entre el balance de líquidos, la lesión renal aguda y la mortalidad en pacientes con choque séptico. Métodos: Se realizó un estudio de casos y controles en una unidad de terapia intensiva pediátrica. Se comparó el balance de líquidos en las primeras 72 h y la presencia de lesión renal aguda en pacientes con diagnóstico de choque séptico que fallecieron contra pacientes que sobrevivieron a la misma patología. Se realizó un análisis univariado y multivariado. Resultados: Se incluyeron 45 casos y 45 controles en el análisis. La mortalidad se asoció con riesgo pediátrico de mortalidad (PRISM) ≥ 26 puntos (RM 7.5, IC 95% 2.8-18.7; p = 0.000), disfunción orgánica logística pediátrica (PELOD) ≥ 24 puntos (RM 11.0, IC 95% 4.1-29.4; p = 0.000), creatinina ≥ 0.65 mg/dl (RM 5.6, IC 95% 2.2-13.9; p = 0.000), lactato ≥ 2.5 mmol/l (RM 2.5, IC 95% 1.1-5.9; p = 0.033), SvO2 < 60% (RM 4.6, IC 95% 4.5-4.5; p = 0.001), balance positivo > 9% en 72 h (RM 4.3, IC 95% 1.6-11.7; p = 0.003), lesión renal aguda (RM 5.7, IC 95% 2.2-15.1; p = 0.000). En el modelo multivariado, PRISM ≥ 26 y PELOD ≥ 24 puntos permanecieron significativas. Conclusiones: En los pacientes que fallecieron por choque séptico, el modelo multivariado mostró una asociación con PRISM ≥26 y PELOD ≥24 y una tendencia hacia la asociación con SvO2 <60% y balance de líquidos positivo >9%.

Abstract: Background: In patients with septic shock, excessive fluid administration can lead to increased morbidity and mortality. The aim of this study was to evaluate the association between fluid balance, acute kidney injury and mortality in patients with septic shock. Methods: A study of cases and controls was conducted in a Pediatric Intensive Care Unit. The fluid balance in the first 72 h and the presence of acute kidney injury was compared in patients diagnosed with septic shock who died against patients who survived the same condition. Univariate and multivariate analyses were performed. Results: Forty-five cases and forty-five controls were included in the analysis. Mortality was associated with Pediatric Risk of Mortality (PRISM III) ≥ 26 points (OR 7.5, 95% CI 2.8-18.7; p = 0.000), Pediatric Logistic Organ Dysfunction (PELOD) ≥ 24 points (OR 11.0, 95% CI 4.1-29.4; p = 0.000), creatinine ≥ 0.65 mg/dl (OR 5.6, 95% CI 2.2-13.9; p = 0.000), lactate ≥ 2.5 mmol/l (OR 2.5, 95% CI 1.1-5.9; p = 0.033), SvO2 < 60% (OR 4.6, 95% CI 4.5-4.5; p = 0.001), positive balance > 9% in 72 h (OR 4.3, 95% CI 1.6-11.7; p = 0.003), acute kidney injury (OR 5.7, 95% CI: 2.2-15.1; p = 0.000). In the multivariate model, the values of PRISM ≥26 and PELOD ≥24 points were significant. Conclusions: In patients who died due to septic shock, the multivariate model showed an association with PRISM ≥26 and PELOD ≥24 and a trend toward association with SvO2 <60% and positive balance of liquids > 9%.

Iron responsive-like elements in the parasite Entamoeba histolytica.

In Entamoeba histolytica, iron modulates virulence and gene expression via unknown regulatory mechanisms. The existence of a posttranscriptional iron regulatory system parallel with the iron-responsive element (IRE)/iron regulatory protein (IRP) system in the protozoan Trichomonas vaginalis has recently been reported. Due to their evolutionary closeness and the importance of iron for growth and virulence in these protozoa, we hypothesized the existence of an IRE/IRP-like mechanism in E. histolytica. To determine the presence of IRE-like elements in some mRNAs from this parasite, we performed in silico analyses of the 5'- and 3'-UTRs of mRNAs encoding virulence factors and cytoskeleton, ribosomal and metabolism proteins. The Zuker mfold software predicted IRE-like secondary structures in 52 of the 135 mRNAs analysed. However, only nine structures shared sequence similarity with the apical loop sequence (CAGUGN) of the previously reported human IRE-ferritin, whereas the GUU/UUG protozoan-specific motif was detected in 23 stem-loop structures. A new motif, AUU/AUUU, was also observed in 23 structures, suggesting the possible existence of an amoeba-specific motif. Additionally, cross-linking and RNA electrophoretic mobility shift assays showed specific RNA-protein interactions, using as a model two amoebic IRE-like elements from iron-regulated mRNAs and HeLa, T. vaginalis and E. histolytica cytoplasmic proteins. Our data suggest the presence of a posttranscriptional iron regulatory IRE/IRP-like mechanism in E. histolytica.