The Combined Antioxidant Effects of N-Acetylcysteine, Vitamin D3, and Glutathione from the Intestinal-Neuronal In Vitro Model.

Chronic oxidative stress has been consistently linked to age-related diseases, conditions, and degenerative syndromes. Specifically, the brain is the organ that significantly contributes to declining quality of life in ageing. Since the body cannot completely counteract the detrimental effects of oxidative stress, nutraceuticals' antioxidant properties have received significant attention in recent years. This study assesses the potential health benefits of a novel combination of glutathione, vitamin D3, and N-acetylcysteine. To examine the combination's absorption and biodistribution and confirm that it has no harmful effects, the bioavailability of the mixture was first evaluated in a 3D model that mimicked the intestinal barrier. Further analyses on the blood-brain barrier was conducted to determine the antioxidant effects of the combination in the nervous system. The results show that the combination reaches the target and successfully crosses the blood-brain and intestinal barriers, demonstrating enhanced advantages on the neurological system, such as a reduction (about 10.5%) in inflammation and enhancement in cell myelination (about 20.4%) and brain tropism (about 18.1%) compared to the control. The results support the cooperative effect of N-acetylcysteine, vitamin D3, and glutathione to achieve multiple health benefits, outlining the possibility of an alternative nutraceutical approach.

Enhancing Vitamin D3 Efficacy: Insights from Complexation with Cyclodextrin Nanosponges and Its Impact on Gut-Brain Axes in Physiology and IBS Syndrome.

Vitamin D3 (VitD3) plays a crucial role in various cellular functions through its receptor interaction. The biological activity of Vitamin D3 can vary based on its solubility and stability. Thus, the challenge lies in maximizing its biological effects through its complexation within cyclodextrin (ßNS-CDI 1:4) nanosponges (NS) (defined as VitD3NS). Therefore, its activity has been evaluated on two different gut-brain axes (healthy gut/degenerative brain and inflammatory bowel syndrome gut/degenerative brain axis). At the gut level, VitD3-NS mitigated liposaccharide-induced damage (100 ng/mL; for 48 h), restoring viability, integrity, and activity of tight junctions and reducing ROS production, lipid peroxidation, and cytokines levels. Following intestinal transit, VitD3-NS improved the neurodegenerative condition in the healthy axis and the IBS model, suggesting the ability of VitD3-NS to preserve efficacy and beneficial effects even in IBS conditions. In conclusion, this study demonstrates the ability of this novel form of VitD3, named VitD3-NS, to act on the gut-brain axis in healthy and damaged conditions, emphasizing enhanced biological activity through VitD3 complexation, as such complexation increases the beneficial effect of vitamin D3 in both the gut and brain by about 50%.

Effects of Nutraceutical Compositions Containing Rhizoma Gastrodiae or Lipoic Acid in an In Vitro Induced Neuropathic Pain Model.

BACKGROUND: Peripheral neuropathy is caused by a malfunction in the axons and myelin sheaths of peripheral nerves and motor and sensory neurons. In this context, nonpharmacological treatments with antioxidant potential have attracted much attention due to the issues that some conventional pharmaceutical therapy can generate. Most of these treatments contain lipoic acid, but issues have emerged regarding its use. Considering this, the present study evaluated the beneficial effects of nutraceuticals based on Gastrodiae elata dry extract 10:1 or lipoic acid in combination with other substances (such as citicholine, B vitamins, and acetyl L-carnitine). METHOD: To assess the combination's absorption and biodistribution and exclude cytotoxicity, its bioavailability was first examined in a 3D intestinal barrier model that replicated oral ingestion. Subsequently, a 3D model of nerve tissue was constructed to investigate the impacts of the new combination on the significant pathways dysregulated in peripheral neuropathy. RESULTS: Our findings show that the novel combination outperformed in initial pain relief response and in recovering the mechanism of nerve healing following Schwann cell injury by successfully crossing the gut barrier and reaching the target site. CONCLUSION: This article describes a potential alternative nutraceutical approach supporting the effectiveness of combinations with Gastrodiae elata extract in decreasing neuropathy and regulating pain pathways.

The Role of Bifidobacterium bifidum novaBBF7, Bifidobacterium longum novaBLG2 and Lactobacillus paracasei TJB8 to Improve Mechanisms Linked to Neuronal Cells Protection against Oxidative Condition in a Gut-Brain Axis Model.

Despite the identification of several innovative targets for avoiding cognitive decline, there has yet to be a widely accepted approach that deals with minimising the deterioration of cognitive function. In this light, recent studies suggest that regulating the gut-brain axis with probiotics is a potential therapeutic strategy to support brain health. For this reason, in vitro models were used to examine the efficacy of different probiotic combinations to enhance intestinal homeostasis and positively affect the brain. Therefore, the new formulation has been evaluated for its capacity to modify intestinal barrier functions in a 3D in vitro model without any adverse effects and directly impact the mechanisms underlying cognitive function in a gut-brain axis model. According to our findings, B. bifidum novaBBF7 10 mg/mL, B. longum novaBLG2 5 mg/mL and L. paracasei TJB8 10 mg/mL may successfully modify the intestinal barrier and improve SCFA production. Successively, the probiotics studied caused no harm at the neuronal level, as demonstrated by iNOS, mitochondrial potential, and cell viability tests, confirming their safety features and enhancing antioxidant mechanisms and antineuroinflammation activity. Additionally, the damage caused by oxidative stress was also healed, and critical pathways that result in cognitive impairment were changed by synergetic action, supporting the hypothesis that brain ageing and neurodegeneration are slowed down. All these findings demonstrate the ability of probiotics to affect cognitive processes and their ability to sustain the mechanisms underlying cognitive function by acting on intestinal function.

Novel Approach to the Treatment of Neuropathic Pain Using a Combination with Palmitoylethanolamide and Equisetum arvense L. in an In Vitro Study.

Neuropathic pain is a typical patient disorder resulting from damage and dysfunction of the peripheral neuraxis. Injury to peripheral nerves in the upper extremities can result in a lifelong reduction in quality of life and a devastating loss of sensory and motor function. Since some standard pharmaceutical therapies can cause dependence or intolerance, nonpharmacological treatments have gained great interest in recent years. In this context, the beneficial effects of a new combination of palmitoylethanolamide and Equisetum arvense L. are evaluated in the present study. The bioavailability of the combination was initially analyzed in a 3D intestinal barrier simulating oral intake to analyze its absorption/biodistribution and exclude cytotoxicity. In a further step, a 3D nerve tissue model was performed to study the biological effects of the combination during the key mechanisms leading to peripheral neuropathy. Our results demonstrate that the combination successfully crossed the intestinal barrier and reached the target site, modulating the nerve recovery mechanism after Schwann cell injury and offering the initial response of relieving pain. This work supported the efficacy of palmitoylethanolamide and Equisetum arvense L. in reducing neuropathy and modifying the major pain mechanisms, outlining a possible alternative nutraceutical approach.

Developing New Cyclodextrin-Based Nanosponges Complexes to Improve Vitamin D Absorption in an In Vitro Study.

Vitamin D plays an important role in numerous cellular functions due to the ability to bind the Vitamin D receptor (VDR), which is present in different tissues. Several human diseases depend on low vitamin D3 (human isoform) serum level, and supplementation is necessary. However, vitamin D3 has poor bioavailability, and several strategies are tested to increase its absorption. In this work, the complexation of vitamin D3 in Cyclodextrin-based nanosponge (CD-NS, in particular, ßNS-CDI 1:4) was carried out to study the possible enhancement of bioactivity. The ßNS-CDI 1:4 was synthesized by mechanochemistry, and the complex was confirmed using FTIR-ATR and TGA. TGA demonstrated higher thermostability of the complexed form. Subsequently, in vitro experiments were performed to evaluate the biological activity of Vitamin D3 complexed in the nanosponges on intestinal cells and assess its bioavailability without cytotoxic effect. The Vitamin D3 complexes enhance cellular activity at the intestinal level and improve its bioavailability. In conclusion, this study demonstrates for the first time the ability of CD-NS complexes to improve the chemical and biological function of Vitamin D3.

Effects of Usnic Acid to Prevent Infections by Creating a Protective Barrier in an In Vitro Study.

Nasal sprays are medical devices useful for preventing infection and the subsequent spread of airborne pathogens. The effectiveness of these devices depends on the activity of chosen compounds which can create a physical barrier against viral uptake as well as incorporate different substances with antiviral activity. Among antiviral compounds, UA, a dibenzofuran derived from lichens, has the mechanical ability to modify its structure by creating a branch capable of forming a protective barrier. The mechanical ability of UA to protect cells from virus infection was investigated by analyzing the branching capacity of UA, and then the protection mechanism in an in vitro model was also studied. As expected, UA at 37 °C was able to create a barrier confirming its ramification property. At the same time, UA was able to block the infection of Vero E6 and HNEpC cells by interfering with a biological interaction between cells and viruses as revealed also by the UA quantification. Therefore, UA can block virus activity through a mechanical barrier effect without altering the physiological nasal homeostasis. The findings of this research could be of great relevance in view of the growing alarm regarding the spread of airborne viral diseases.

New Hyaluronic Acid from Plant Origin to Improve Joint Protection-An In Vitro Study.

BACKGROUND: In recent decades, hyaluronic acid (HA) has attracted great attention as a new treatment option for osteoarthritis. Classical therapies are not able to stop the cartilage degeneration process nor do they favor tissue repair. Nowadays, it is accepted that high molecular weight HA can reduce inflammation by promoting tissue regeneration; therefore, the aim of this study was to verify the efficacy of a new high molecular weight HA of plant origin (called GreenIuronic®) in maintaining joint homeostasis and preventing the harmful processes of osteoarthritis. METHODS: The bioavailability of GreenIuronic® was investigated in a 3D intestinal barrier model that mimics human oral intake while excluding damage to the intestinal barrier. Furthermore, the chemical significance and biological properties of GreenIuronic® were investigated in conditions that simulate osteoarthritis. RESULTS: Our data demonstrated that GreenIuronic® crosses the intestinal barrier without side effects as it has a chemical-biological profile, which could be responsible for many specific chondrocyte functions. Furthermore, in the osteoarthritis model, GreenIuronic® can modulate the molecular mechanism responsible for preventing and restoring the degradation of cartilage. CONCLUSION: According to our results, this new form of HA appears to be well absorbed and distributed to chondrocytes, preserving their biological activities. Therefore, the oral administration of GreenIuronic® in humans can be considered a valid strategy to obtain beneficial therapeutic effects during osteoarthritis.

Polyphenol-Rich Larix decidua Bark Extract with Antimicrobial Activity against Respiratory-Tract Pathogens: A Novel Bioactive Ingredient with Potential Pharmaceutical and Nutraceutical Applications.

Larch (Larix decidua) bark is a sawmill waste, traditionally used for antiseptic, expectorant and dermatological (wound healing, eczema, psoriasis) purposes. In this work, we developed a food-grade dry larch bark extract (LBE) from sawmill by-products using hydro-alcoholic extraction. The antibacterial activity of LBE was evaluated against respiratory-tract pathogens, i.e., Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa and Haemophilus influenza, and it was compared to that of grapefruit seed extract (GSE), a commercially available raw material commonly proposed as antibacterial ingredient for over-the-counter products. Procyanidins (PACs) and other polyphenols contents in LBE were determined by HPLC-FLD-MS and HPLC-DAD-MSn, respectively. The antimicrobial activity of LBE and GSE was assessed using the micro-plate dilution technique in concentration range of 2-200 µg/mL, and the safety of these dosages was assessed in cellular and animal models. LBE showed considerable contents of PACs (15% w/w; especially B-type) and other polyphenols (3.8% w/w), among which the characteristic spiropolyphenols larixinol and epilarixinol were identified, together with the flavonoids isoquercitrin and rutin, already reported as growth inhibitors of different respiratory-tract pathogens. LBE showed higher antimicrobial activity compared to GSE, demonstrated by a growth inhibition range of 10-40% towards five of six strains tested, compared to 10-15% of GSE. These results suggest that LBE may represent a natural and sustainable source of active compounds with antibacterial activity for pharmaceutical and nutraceutical applications.

Anemia in patients with Covid-19: pathogenesis and clinical significance.

COVID-19 patients typically present with lower airway disease, although involvement of other organ systems is usually the rule. Hematological manifestations such as thrombocytopenia and reduced lymphocyte and eosinophil numbers are highly prevalent in COVID-19 and have prognostic significance. Few data, however, are available about the prevalence and significance of anemia in COVID-19. In an observational study, we investigated the prevalence, pathogenesis and clinical significance of anemia among 206 patients with COVID-19 at the time of their hospitalization in an Internal Medicine unit. The prevalence of anemia was 61% in COVID-19, compared with 45% in a control group of 71 patients with clinical and laboratory findings suggestive of COVID-19, but nasopharyngeal swab tests negative for SARS-CoV-2 RNA (p = 0.022). Mortality was higher in SARS-CoV-2 positive patients. In COVID-19, females had lower hemoglobin concentration than males and a higher prevalence of moderate/severe anemia (25% versus 13%, p = 0.032). In most cases, anemia was mild and due to inflammation, sometimes associated with iron and/or vitamin deficiencies. Determinants of hemoglobin concentration included: erythrocyte sedimentation rate, serum cholinesterase, ferritin and protein concentrations and number of chronic diseases affecting each patient. Hemoglobin concentration was not related to overall survival that was, on the contrary, influenced by red blood cell distribution width, age, lactate dehydrogenase and the ratio of arterial partial oxygen pressure to inspired oxygen fraction. In conclusion, our results highlight anemia as a common manifestation in COVID-19. Although anemia does not directly influence mortality, it usually affects elderly, frail patients and can negatively influence their quality of life.

Redo procedures and chronic renal dysfunction are associated with higher risk of cardiac electronic device infections.

BACKGROUND: Infection is a major complication of pacemaker (PM) and implantable cardioverter-defibrillator (ICD) implantation. The present study sought to analyze the incidence rate of device infections, to investigate possible relationships between first implantations/repeated procedures and infection rates, and to identify some main risk factors associated with infection of cardiac implantable electronic devices (CIED). METHODS: In a single center retrospective observational study, records of 3899 consecutive patients having undergone PM and ICD implantation, cardiac resynchronization therapy (CRT) or revision (device/lead replacements or upgrades) and between 2002 and 2012 were obtained. RESULTS: Over a mean follow-up period of 66±14 months, a total of 50 patients were identified as having CIED infection (0.85% per procedure and 1.28% per patient). Chronic renal dysfunction and repeated procedures were independently associated with higher risk of CIED infection on multivariate analysis (respectively, OR 1.30, 95% CI: 1.16-1.57, P<0.0001; OR 1.23, 95% CI: 1.12-1.42, P<0.0001). Staphylococcal species was responsible for the bulk of CIED infections (70% of all positive cultures). Coagulase-negative staphylococci were found more frequently than staphylococcus aureus (30% vs. 12%). CONCLUSIONS: The infection rate after cardiac electronic device procedures was low over the follow-up period. Repeated procedures and chronic renal dysfunction were associated with higher risk of CIED infection. Staphylococcal species were mainly responsible for device infections.

Larix decidua Bark as a Source of Phytoconstituents: An LC-MS Study.

Larix decidua bark is a waste of the timber industry and is widely diffused in Northern Italy. This material can be considered a good source of antioxidants and phytoconstituents with possible use in cosmetic or nutraceutical products. In this study, simple extraction of larch bark was performed using mixtures of ethanol/water. Furthermore, the phytochemical composition of larch bark extract was studied using LC-MSn methods and the main constituents were identified as flavonoids, spiro-polyphenols, and procyanidins. To confirm the identification by LC-MS semi-preparative HPLC was performed in order to isolate the main constituents and verify the structures by ¹H-NMR. Antioxidant properties were studied using an in vitro approach combining DPPH assay and LC-MS in order to establish different roles of the various classes of phytochemicasl of the extract. DPPH activity of some of the isolated compounds was also assessed. The overall results indicate this waste material as a good source of antioxidant compounds, mainly procyanidins, whichresulted the most active constituents in the DPPH assay.

Lung ultrasound in internal medicine: A bedside help to increase accuracy in the diagnosis of dyspnea.

BACKGROUND: Dyspnea is one of the most frequent causes of admission in Internal Medicine wards, leading to a sizeable utilization of medical resources. STUDY DESIGN AND METHODS: The role of bedside lung ultrasound (LUS) was evaluated in 130 consecutive patients (age: 81±9years), in whom blindly collected LUS results were compared with data obtained by clinical examination, medical history, blood analysis, and chest X-ray. Dyspnea etiology was classified as "cardiac" (n=80), "respiratory" (n=36) or "mixed" (n=14), according to the discharge diagnosis (congestive heart failure either alone [n=80] or associated with pneumonia [n=14], pneumonia [n=24], and obstructive disventilatory syndrome [n=12]). An 8-window LUS protocol was applied to evaluate B-line distribution, "interstitial syndrome" pattern, pleural effusion and images of static or dynamic air bronchogram/focal parenchymal consolidation. RESULTS: The presence of a generalized "interstitial syndrome" at the initial LUS evaluation allowed to discriminate "cardiac" from "pulmonary" Dyspnea with high sensitivity (93.75%; confidence intervals: 86.01%-97.94%) and specificity (86.11%; 70.50%-95.33%). Positive and negative predictive values were 93.76% (86.03%-97.94%) and 86.09% (70.47%-95.32%), respectively. Moreover, LUS diagnostic accuracy for the diagnosis of pneumonia was not inferior to that of chest X-ray. CONCLUSIONS: Bedside LUS evaluation contributes with high sensitivity and specificity to the differential diagnosis of Dyspnea. This holds true not only in the emergency setting, but also in the sub-acute Internal Medicine arena. A wider use of this portable technique in our wards is warranted.

Phytochemical investigations and antiproliferative secondary metabolites from Thymus alternans growing in Slovakia.

CONTEXT: Thymus alternans Klokov (Lamiaceae) is a neglected species of the genus Thymus (Sect. Serpyllum) endemic to Carpathian area, where it is used as a flavouring agent and for medicinal purposes. OBJECTIVE: The aim of the work was to identify antiproliferative constituents from the flowering aerial parts of this plant. MATERIALS AND METHODS: Thymus alternans extracts were analyzed by HPLC-MSn and subjected to extensive chromatographic separations. The isolated compounds (phenolics and triterpenes) were structurally elucidated by MS and 1D and 2D NMR experiments. Essential oil (EO) composition was determined by GC-FID and GC-MS. Six purified triterpenes and EO were assayed for in vitro antiproliferative activity against a panel of human cancer cells, namely, breast (MDA-MB 231), colon (HCT-15 and HCT116), lung (U1810), pancreatic (BxPC3), melanoma (A375) and cervical carcinoma (A431) cells. RESULTS: The structures of the isolated compounds were achieved on the basis of H-NMR and MS experiments. Luteolin-4'-O-ß-d-glucopyranoside (P1), chrysoeriol-7-O-ß-d-glucopyranoside (P2), chrysoeriol-5-O-ß-d-glucopyranoside (P3), apigenin-7-O-ß-d-glucopyranoside (P4), rosmarinic acid (P5), rosmarinic acid-3'-O-ß-d-glucopyranoside (P6), caffeic acid-3-O-ß-d-glucopyranoside (P7), 3α-hydroxy-urs-12,15-diene (T1), α-amyrin (T2), ß-amyrin (T3), isoursenol (T4), epitaraxerol (T5), and oleanolic acid (T6). GC-MS analysis revealed that the EO of T. alternans was devoid of phenols and belonged to the nerolidol-chemotype, that is typical of the Sect. Serpyllum. The six purified triterpenes (T1-T6) were active with IC50 ranging from 0.5 to 5 µM being comparable or better than those of reference compounds betulinic acid and cisplatin. The EO exhibited significant effects on A375, MDA-MB 231 and HCT116 cell lines with IC50 in the range of 5-8 µg/mL. CONCLUSION: The reported results suggest that T. alternans can be considered as a good source of phytoconstituents with possible importance in the pharmaceutical field.

Managing a Mass CO Poisoning: Critical Issues and Solutions From the Field to the Hyperbaric Chamber.

Carbon monoxide acute intoxication is a common cause of accidental poisoning in industrialized countries and sometimes it produces a real mass casualty incident. The incident described here occurred in a church in the province of Verona, when a group of people was exposed to carbon monoxide due to a heating system malfunction. Fifty-seven people went to the Emergency Department. The mean carboxyhemoglobin (COHb) level was 10.1±5.7% (range: 3-25%). The clinicians, after medical examination, decided to move 37 patients to hyperbaric chambers for hyperbaric oxygen (HBO) therapy. This is the first case report that highlights and analyses the logistic difficulties of managing a mass carbon monoxide poisoning in different health care settings, with a high influx of patients in an Emergency Department and a complex liaison between emergency services. This article shows how it is possible to manage a complex situation with good outcome. (Disaster Med Public Health Preparedness. 2017;11:251-255).

Secondary Metabolites of Alchemilla persica Growing in Iran (East Azarbaijan).

Phytochemical investigations of Alchemilla persica Rothm. growing in Iran were performed taking into account both the volatile and polar constituents. The hydrodistilled essential oil was analysed by GC-MS that revealed the presence of alkanes (27.8%), diterpenoids (19.6%) and sesquiterpene hydrocarbons (17.1%) as the major constituents, while tannins and flavonol glycosides were identified as the most abundant constituents of the methanol extract by HPLC-MS. A. persica can be a valuable source of ellagitannins and polyphenols.

Time-series analysis for online recognition and localization of sick pig (Sus scrofa) cough sounds.

This paper considers the online localization of sick animals in pig houses. It presents an automated online recognition and localization procedure for sick pig cough sounds. The instantaneous energy of the signal is initially used to detect and extract individual sounds from a continuous recording and their duration is used as a preclassifier. Autoregression (AR) analysis is then employed to calculate an estimate of the sound signal, and the parameters of the estimated signal are subsequently evaluated to identify the sick cough sounds. It is shown that the distribution of just three AR parameters provides an adequate classifier for sick pig coughs. A localization technique based on the time difference of arrival is evaluated on field data and is shown that it is of acceptable accuracy for this particular application. The algorithm is applied on continuous recordings from a pig house to evaluate its effectiveness. The correct identification ratio ranged from 73% (27% false positive identifications) to 93% (7% false positive identifications) depending on the position of the microphone that was used for the recording. Although the false negative identifications are about 50% it is shown that this accuracy can be enough for the purpose of this tool. Finally, it is suggested that the presented application can be used to online monitor the welfare in a pig house, and provide early diagnosis of a cough hazard and faster treatment of sick animals.

Oral administration of yessotoxin stabilizes E-cadherin in mouse colon.

YTX has been shown to disrupt the E-cadherin-catenin system in cultured epithelial cells, raising some concern that ingestion of seafood contaminated by YTX might favour tumour spreading and metastasis formation in vivo. In order to probe whether YTX might affect cadherin systems in vivo, we have set up a study involving repeated oral dosing of the toxin in mice (1mg/kg/day, for 7 days) and analysis of E-cadherin and N-cadherin in tissue extracts obtained at the end of the dosing scheme, as well as 1 and 3 months after YTX administration. We found that the E-cadherin pools obtained from lung and kidney were not altered by YTX in any of our experimental conditions. Extracts from mouse colon contained intact E-cadherin and an E-cadherin fragment of about 90 kDa (ECRA(90)), displaying a molecular alteration resembling that caused by YTX in cultured cells. We found that the relative proportion of ECRA(90), as compared to intact E-cadherin, was higher in colon extracts from control mice than from YTX-treated animals, indicating that oral administration of YTX to mice stabilizes E-cadherin of mouse colon. No significant difference could be detected in samples prepared from colons obtained 30 or 90 days after termination of YTX treatment. Oral administration of YTX to mice did not lead to a significant increase in the fragments of E-cadherin detectable in serum, neither it altered the N-cadherin pool of mouse heart. Electron microscopy analysis showed no substantial ultrastructural differences between controls and YTX-treated mice. Our findings show that ingestion of food contaminated by YTX poses a low risk of disruption of the E-cadherin system in vivo.

Structure-activity relationships of yessotoxins in cultured cells.

The structure-activity relationship of yessotoxins (YTX) has been probed by measuring the potency of several YTX analogues to cause the accumulation of a 100 kDa MW fragment of E-cadherin in MCF-7 breast cancer cells. Under our experimental conditions, the EC(50) of YTX, the reference compound, was 0.55 nM. The introduction of a methylene unit adjacent to one of the sulfate groups, as is the case with the homoyessotoxin molecule, did not appear to greatly affect the potency of the analogue, as the measured EC(50) for this compound was 0.62 nM. The EC(50) values we measured for 45-hydroxyhomoyessotoxin and carboxyyessotoxin were about 9.4 and 26 nM, respectively, whereas the EC(50) of noroxoyessotoxin, lacking most of the C(9) chain, was about 50 nM. Thus, significant differences in the potencies of YTX analogues were found when structural changes involved the C(9) terminal chain of these compounds, leading to the conclusion that this portion of the molecule is essential for the activity of YTX in MCF-7 cells. A comparison of our findings with available information regarding the potency of YTX and its analogues in other experimental systems shows that the EC(50)'s we measured for the different compounds are up to 200-fold lower and vary in a wider concentration range. We speculate that YTX effects could involve two separate receptorial systems.