Placing CF2 in the Center: Major Physicochemical Changes Upon a Minor Structural Alteration in Gem-Difunctional Compounds.

Fluorine atoms play an important role in all branches of chemistry and accordingly, it is very important to study their unique and varied effects systematically, in particular, the structure-physicochemical properties relationship. The present study describes exceptional physicochemical effects resulting from a H/F exchange at the methylene bridge of gem-difunctional compounds. The Δlog P(CF2-CH2) values, that is, the change in lipophilicity, observed for the CH2 /CF2 replacement in various α,α-phenoxy- and thiophenoxy-esters/amides, diketones, benzodioxoles and more, fall in the range of 0.6-1.4 units, which for most cases, is far above the values expected for such a replacement. Moreover, for compounds holding more than one such gem-difunctional moiety, the effect is nearly additive, so one can switch from a hydrophilic compound to a lipophilic one in a limited number of H/F exchanges. DFT studies of some of these systems revealed that polarity, conformational preference as well as charge distributions are strongly affected by such hydrogen to fluorine atom substitution. The pronounced effects described, are a result of the interplay between changes in polarity, H-bond basicity and molecular volume, which were obtained with a very low 'cost' in terms of molecular weight or steric effects and may have a great potential for implementation in various fields of chemical sciences.

Pathophysiological profile of awake and anesthetized pigs following systemic exposure to the highly lethal ricin toxin.

Ricin, a plant-derived toxin originating from the seeds of Ricinus communis (castor bean plant), is one of the most lethal toxins known. To date, no in-depth study of systemic exposure to ricin in a standardized large animal model has been reported. This study details for the first time the pathophysiological hemodynamic profile following systemic/intramuscular exposure to the ricin toxin in a porcine model by comprehensive cardiorespiratory monitoring of awake and anesthetized pigs. Unlike respiratory exposure to ricin, which is characterized by the development of acute respiratory distress syndrome, following intramuscular exposure to ricin respiratory parameters were grossly unaffected, however the hemodynamics of both awake and anesthetize pigs were unsustainably compromised. We show that in the early phase until approximately 24 h post-exposure, cardiac output is not impaired although one of its components, stroke volume, is relatively low. This is due to compensatory increase in heart rate, which eventually becomes insufficient. Later, distributive shock develops, characterized by severe vasodilatation (decreased systemic vascular resistance), low central venous oxygen saturation and elevation of venous-to-arterial carbon dioxide difference indicating increase in tissue oxygen demand not met by cardiac supply. These findings serve as a basis for further studies to evaluate the ability of supportive treatments such as vasoactive and inotropic drugs, to postpone the hemodynamic deterioration and thus expand the therapeutic window for the anti-ricin treatment. Such studies are of crucial importance for judicious treatment of victims of acts of bioterrorism or of intentional self-poisoning.

Poly(vinyl alcohol)-methacrylate with CRGD peptide: A photocurable biocompatible hydrogel.

Polyvinyl alcohol (PVA)-based hydrogels are promising biomaterials for tissue engineering printing applications. However, one of their main disadvantages is their inability to support cell attachment, which is a critical feature for the preparation of biological scaffolds. The goal of this study was to develop a printable, cell-supportive PVA-based bioink with tunable mechanical properties, without using animal-derived polymers which potentially harbor human pathogens. An ultraviolet light (UV) curable PVA-methacrylate (PVA-MA) polymer mixed with Cys-Arg-Gly-Asp (CRGD) peptide was developed. This peptide holds the integrin receptor binding sequence - RGD, that can enhance cell attachment. The additional cysteine was designed to enable its thiol binding under UV to methacrylate groups of the UV curable PVA-MA. Vero cell, as an adherent cell model was used to assess the hydrogel's cell adhesion. It was found that the PVA-MA-CRGD formula enables the preparation of hydrogels with excellent cell attachment and had even shown superior cell attachment properties relative to added gelatin. Adding hyaluronic acid (HA) as a rheologic modulator enabled the printing of this new formula. Our overall data demonstrates the applicability of this mixture as a bioink for soft tissue engineering such as skin, adipose, liver or kidney tissue.

Intramuscular Exposure to a Lethal Dose of Ricin Toxin Leads to Endothelial Glycocalyx Shedding and Microvascular Flow Abnormality in Mice and Swine.

Ricin toxin isolated from the castor bean (Ricinus communis) is one of the most potent and lethal molecules known. While the pathophysiology and clinical consequences of ricin poisoning by the parenteral route, i.e., intramuscular penetration, have been described recently in various animal models, the preceding mechanism underlying the clinical manifestations of systemic ricin poisoning has not been completely defined. Here, we show that following intramuscular administration, ricin bound preferentially to the vasculature in both mice and swine, leading to coagulopathy and widespread hemorrhages. Increased levels of circulating VEGF and decreased expression of vascular VE-cadherin caused blood vessel impairment, thereby promoting hyperpermeability in various organs. Elevated levels of soluble heparan sulfate, hyaluronic acid and syndecan-1 were measured in blood samples following ricin intoxication, indicating that the vascular glycocalyx of both mice and swine underwent extensive damage. Finally, by using side-stream dark field intravital microscopy imaging, we determined that ricin poisoning leads to microvasculature malfunctioning, as manifested by aberrant blood flow and a significant decrease in the number of diffused microvessels. These findings, which suggest that glycocalyx shedding and microcirculation dysfunction play a major role in the pathology of systemic ricin poisoning, may serve for the formulation of specifically tailored therapies for treating parenteral ricin intoxication.

Modulation of the H-Bond Basicity of Functional Groups by α-Fluorine-Containing Functions and its Implications for Lipophilicity and Bioisosterism.

Modulation of the H-bond basicity (pKHB) of various functional groups (FGs) by attaching fluorine functions and its impact on lipophilicity and bioisosterism considerations are described. In general, H/F replacement at the α-position to H-bond acceptors leads to a decrease of the pKHB value, resulting, in many cases, in a dramatic increase in the compounds' lipophilicity (log Po/w). In the case of α-CF2H, we found that these properties may also be affected by intramolecular H-bonds between CF2H and the FG. A computational study of ketone and sulfone series revealed that α-fluorination can significantly affect overall polarity, charge distribution, and conformational preference. The unique case of α-di- and trifluoromethyl ketones, which exist in octanol/water phases as ketone, hemiketal, and gem-diol forms, in equilibrium, prevents direct log Po/w determination by conventional methods, and therefore, the specific log Po/w values of these species were determined directly, for the first time, using Linclau's 19F NMR-based method.

Mechanical Ventilation with Room Air is Feasible in a Moderate Acute Respiratory Distress Syndrome Pig Model - Implications for Disaster Situations and Low-Income Nations.

INTRODUCTION: Patients with respiratory failure are usually mechanically ventilated, mostly with fraction of inspired oxygen (FiO2) > 0.21. Minimizing FiO2 is increasingly an accepted standard. In underserved nations and disasters, salvageable patients requiring mechanical ventilation may outstrip oxygen supplies. STUDY OBJECTIVE: The hypothesis of the present study was that mechanical ventilation with FiO2 = 0.21 is feasible. This assumption was tested in an Acute Respiratory Distress Syndrome (ARDS) model in pigs. METHODS: Seventeen pigs were anesthetized, intubated, and mechanically ventilated with FiO2 = 0.4 and Positive End Expiratory Pressure (PEEP) of 5cmH2O. Acute Respiratory Distress Syndrome was induced by intravenous (IV) oleic acid (OA) infusion, and FiO2 was reduced to 0.21 after 45 minutes of stable moderate ARDS. If peripheral capillary oxygen saturation (SpO2) decreased below 80%, PEEP was increased gradually until maximum 20cmH2O, then inspiratory time elevated from one second to 1.4 seconds. RESULTS: Animals developed moderate ARDS (mean partial pressure of oxygen [PaO2]/FiO2 = 162.8, peak and mean inspiratory pressures doubled, and lung compliance decreased). The SpO2 decreased to <80% rapidly after FiO2 was decreased to 0.21. In 14/17 animals, increasing PEEP sufficed to maintain SpO2 > 80%. Only in 3/17 animals, elevation of FiO2 to 0.25 after PEEP reached 20cmH2O was needed to maintain SpO2 > 80%. Animals remained hemodynamically stable until euthanasia one hour later. CONCLUSIONS: In a pig model of moderate ARDS, mechanical ventilation with room air was feasible in 14/17 animals by elevating PEEP. These results in animal model support the potential feasibility of lowering FiO2 to 0.21 in some ARDS patients. The present study was conceived to address the ethical and practical paradigm of mechanical ventilation in disasters and underserved areas, which assumes that oxygen is mandatory in respiratory failure and is therefore a rate-limiting factor in care capacity allocation. Further studies are needed before paradigm changes are considered.

Post-Exposure Anti-Ricin Treatment Protects Swine Against Lethal Systemic and Pulmonary Exposures.

Ricin, a plant-derived toxin originating from the seeds of Ricinus communis (castor bean plant), is one of the most lethal toxins known. To date, there is no approved post-exposure therapy for ricin exposures. This work demonstrates for the first time the therapeutic efficacy of equine-derived anti-ricin F(ab')2 antibodies against lethal pulmonary and systemic ricin exposures in swine. While administration of the antitoxin at 18 h post-exposure protected more than 80% of both intratracheally and intramuscularly ricin-intoxicated swine, treatment at 24 h post-exposure protected 58% of the intramuscular-exposed swine, as opposed to 26% of the intratracheally exposed animals. Quantitation of the anti-ricin neutralizing units in the anti-toxin preparations confirmed that the disparate protection conferred to swine subjected to the two routes of exposure stems from variance between the two models. Furthermore, dose response experiments showed that approximately 3 times lesser amounts of antibody are needed for high-level protection of the intramuscularly compared to the intratracheally intoxicated swine. This study, which demonstrates the high-level post-exposure efficacy of anti-ricin antitoxin at clinically relevant time-points in a large animal model, can serve as the basis for the formulation of post-exposure countermeasures against ricin poisoning in humans.

The Effect of Anesthetic Regimens on Intestinal Absorption of Passively Absorbed Drugs in Rats.

PURPOSE: Different anesthetic regimens are used during single pass intestinal perfusion (SPIP) experiments for the study of intestinal drug absorption in rats. We examined the ketamine/xylazine anesthetic combination to evaluate its influence on drug absorption compared to older regimens. Additionally, we examined whether supplementary analgesia has any effect on drug absorption and the effect of the different anesthetic regimens on induction time and stress response. METHODS: Rats were anesthetized using four different anesthetic regimens; ketamine/midazolam, pentobarbital, ketamine/xylazine and ketamine/xylazine/butorphanol. Three model drugs were administered to rat intestines and Peff was calculated. Stress response was evaluated by quantifying blood corticosterone levels and induction time was recorded. RESULTS: We found absorption under pentobarbital to be higher or similar to absorption under ketamine/midazolam. These results partly correlate with past literature data. Ketamine/xylazine was found to give similar or higher Peff compared to pentobarbital and ketamine/midazolam. Addition of butorphanol did not affect absorption and reduced induction time and stress. CONCLUSIONS: In studies of intestinal drug absorption, the ketamine/xylazine combination is superior to other anesthetic regimens as it is more convenient and seems to affect absorption to a lesser extent. Addition of butorphanol is highly recommended as it did not affect absorption but led to a more effective and less stress inducing experiment.

Effective neutralization of chemical warfare agents (HD, VX) by Me-DABCOF: a small molecule with dual action.

The ability of mono N-methyl-1,4-diazabicyclo[2.2.2]octane fluoride (Me-DABCOF, 1) to act as a bifunctional reagent that effectively and universally neutralizes both the persistent and extremely toxic blister agent HD and the nerve agent VX in nearly neutral aqueous solution, alumina powder or a hydrogel formulation, is described.

CF2H, a Functional Group-Dependent Hydrogen-Bond Donor: Is It a More or Less Lipophilic Bioisostere of OH, SH, and CH3?

The effects of the CF2H moiety on H-bond (HB) acidity and lipophilicity of various compounds, when attached directly to an aromatic ring or to other functions like alkyls, ethers/thioethers, or electron-withdrawing groups, are discussed. It was found that the CF2H group acts as a HB donor with a strong dependence on the attached functional group ( A = 0.035-0.165). Regarding lipophilicity, the CF2H group may act as a more lipophilic bioisostere of OH but as a similar or less lipophilic bioisostere of SH and CH3, respectively, when attached to Ar or alkyl. In addition, the lipophilicity of ethers, sulfoxides, and sulfones is dramatically increased upon CH3/CF2H exchange at the α position. Interestingly, this exchange significantly affects not only the polarity and the volume of the solutes but also their HB-accepting ability, the main factors influencing log Poct. Accordingly, this study may be helpful in the rational design of drugs containing this moiety.

A novel swine model of ricin-induced acute respiratory distress syndrome.

Pulmonary exposure to the plant toxin ricin leads to respiratory insufficiency and death. To date, in-depth study of acute respiratory distress syndrome (ARDS) following pulmonary exposure to toxins is hampered by the lack of an appropriate animal model. To this end, we established the pig as a large animal model for the comprehensive study of the multifarious clinical manifestations of pulmonary ricinosis. Here, we report for the first time, the monitoring of barometric whole body plethysmography for pulmonary function tests in non-anesthetized ricin-treated pigs. Up to 30 h post-exposure, as a result of progressing hypoxemia and to prevent carbon dioxide retention, animals exhibited a compensatory response of elevation in minute volume, attributed mainly to a large elevation in respiratory rate with minimal response in tidal volume. This response was followed by decompensation, manifested by a decrease in minute volume and severe hypoxemia, refractory to oxygen treatment. Radiological evaluation revealed evidence of early diffuse bilateral pulmonary infiltrates while hemodynamic parameters remained unchanged, excluding cardiac failure as an explanation for respiratory insufficiency. Ricin-intoxicated pigs suffered from increased lung permeability accompanied by cytokine storming. Histological studies revealed lung tissue insults that accumulated over time and led to diffuse alveolar damage. Charting the decline in PaO2/FiO2 ratio in a mechanically ventilated pig confirmed that ricin-induced respiratory damage complies with the accepted diagnostic criteria for ARDS. The establishment of this animal model of pulmonary ricinosis should help in the pursuit of efficient medical countermeasures specifically tailored to deal with the respiratory deficiencies stemming from ricin-induced ARDS.

Biphasic cuirass ventilation is better than bag-valve mask ventilation for resuscitation following organophosphate poisoning.

OBJECTIVE: Exposure to organophosphates (OP) may lead to a life threatening cholinergic crisis with death attributed to a rapidly progressive respiratory failure. In a toxicological mass casualty event involving organophosphate exposure, many of the victims may depend on immediate short-term ventilation to overcome the respiratory distress which may exhaust life supporting resources. In addition, the mandatory use of personal protective gear by first responders emphasizes the need for a noninvasive, easy-to-operate ventilation device. Our objective was to assess the efficacy of MRTX, a Biphasic Cuirass Ventilation device, in comparison with standard bag-valve mask ventilation following acute organophosphate poisoning. METHODS: Pigs were exposed to paraoxon poisoning (1.4 LD50), and treated 8 min later with atropine (0.05 mg/kg). The control group received no further support (n = 9), the two experimental groups received ventilation support initiated 15 min post exposure and lasted for 25 min: one group was ventilated with the commonly used bag-valve mask (Mask group, n = 7) and the other was ventilated with the Biphasic Cuirass Ventilation device (Cuirass group, n = 7). Clinical signs and physiological parameters were monitored during the first hour, and mortality up to 24 h post exposure was recorded. RESULTS: No mortality was observed in the Cuirass group following OP poisoning, while mortality in the Control and in the Mask groups was high (67% and 71%, respectively). Mouth excretions of the cuirass-ventilated animals were frothy white as in deep suctioning, as opposed to the clear saliva-like appearance of secretions in the other two groups. No further group differences were recorded. CONCLUSIONS: The noninvasive, easy-to-operate Biphasic Cuirass Ventilation device was effective in reducing OP-induced mortality and might be advantageous in an organophosphate mass casualty event. This finding should be validated in further investigations.

Magnesium sulfate treatment against sarin poisoning: dissociation between overt convulsions and recorded cortical seizure activity.

Sarin, a potent organophosphate cholinesterase inhibitor, induces an array of toxic effects including convulsions. Many antidotal treatments contain anticonvulsants to block seizure activity and the ensuing brain damage. Magnesium sulfate (MGS) is used to suppress eclamptic seizures in pregnant women with hypertension and was shown to block kainate-induced convulsions. Magnesium sulfate was evaluated herein as an anticonvulsant against sarin poisoning and its efficacy was compared with the potent anticonvulsants midazolam (MDZ) and caramiphen (CRM). Rats were exposed to a convulsant dose of sarin (96 µg/kg, im) and 1 min later treated with the oxime TMB4 and atropine to increase survival. Five minutes after initiation of convulsions, MGS, CRM, or MDZ were administered. Attenuation of tonic-clonic convulsions was observed following all these treatments. However, radio-telemetric electro-corticography (ECoG) monitoring demonstrated sustained seizure activity in MGS-injected animals while this activity was completely blocked by MDZ and CRM. This disrupted brain activity was associated with marked increase in brain translocator protein levels, a marker for brain damage, measured 1 week following exposure. Additionally, histopathological analyses of MGS-treated group showed typical sarin-induced brain injury excluding the hippocampus that was partially protected. Our results clearly show that MGS demonstrated misleading features as an anticonvulsant against sarin-induced seizures. This stems from the dissociation observed between overt convulsions and seizure activity. Thus, the presence or absence of motor convulsions may be an unreliable indicator in the assessment of clinical status and in directing adequate antidotal treatments following exposure to nerve agents in battle field or terror attacks.