Pet collars containing tetrachlorvinphos (TCVP): evaluation of the results of torsion and on-animal release studies and implications for post-application consumer exposure and risk analysis

Tetrachlorvinphos (TCVP) is the pesticidal active ingredient found in some flea and tick collars for dogs and cats. Recent studies sponsored by The Hartz Mountain Corporation, confirm the safety of TCVP as an active ingredient in pet collars. Based upon data from these new studies and results previously relied upon by the U.S. Environmental Protection Agency, the following conclusions have been made: Torsion study data clearly indicate that approximately 93% of released formulation from TCVP containing pet collars is in a liquid phase immediately following activation.Further, even more relevant to human health risk analysis associated with post-application exposures, in vivo data from dogs wearing TCVP pet collars definitively document that TCVP dust released from the collar is rapidly absorbed into the sebum. The maximum ratio of dust to liquid was 0.023% dust to 99.977% liquid.In vivo fur data provide scientific evidence confirming that the mechanism of dissemination of TCVP from pet collars is as a liquid suspended or dissolved in the animal's sebum, even though it may be released from the collar as a solid. Thus, potential post-application exposure to TCVP, including immediately following collar placement, is almost entirely to a liquid phase.Based upon EPA's refined and conservative "untrimmed" collar risk assessment, post-application incidental oral hand-to-mouth activity by children aged 1 to <2 years of age results in margins of exposure significantly greater than the level of concern of 1000, and therefore do not present unreasonable health risk.

Immune Mediators Important for a Protective Secondary Response to Babesia microti

Babesia microti (B. microti) is a tick-transmitted protozoan parasite that invades red blood cells. It is the primary cause of human babesiosis in the US. The severity of babesiosis caused by B. microti infection can range from asymptomatic to fatal. Risk factors for severe disease include general immune suppression, advanced age (>50) and lack of a spleen. However, severe disease can occur in the absence of any known risk factors. The degree to which tick-transmitted B. microti infection confers protection from subsequent exposure is largely unexplored. This is an important question as both the prevalence and geographic range of tick-transmitted B. microti infection continues to increase and individuals in endemic regions may have multiple exposures over their lifetime. In the current study we used a mouse model to evaluate the degree to which primary infection with B. microti protected against secondary challenge with the same parasite strain. We show that CD4 T cells, and to a lesser extent B cells, contribute to protection. However, mice exhibited significant protection from secondary parasite challenge even in the absence of either CD4 T cells or B cells. The protection mediated by CD4 T cells did not depend on their production of IFN-γ as mice with a targeted gene deletion for the IFN-γ receptor remained fully protected against secondary challenge. Other factors including inducible nitric oxide synthase (iNOS) and the adaptor protein MyD88, important for toll-like receptors, IL-18 and IL-1 signaling, were not important for protection against primary or secondary challenge with B. microti. Thus, our study shows that resolution of primary infection with B. microti results in robust protection against secondary challenge with parasites, at least in the short term. Further studies are needed to evaluate the length of protection and the degree to which protection is impacted by parasite heterogeneity. Although we show an important role for CD4 T cells in protection against secondary challenge, our results suggest that no single aspect of the immune system is solely responsible for adequate protection against secondary challenge with B. microti.

Hyperthermic Enhancement of Immunotherapy: Findings of In Vitro Modeling

PURPOSE/OBJECTIVE(S)

Despite advancement in understanding and manipulation of immune checkpoint molecules in immunotherapeutic design, limitations in treatment efficacy persist. Strategies to enhance effectiveness include use of multiple immunotherapeutic agents or combination with radiation therapy. Prior studies have also shown potential for hyperthermia to augment response to both of these therapeutic modalities. We hypothesized that in vitro assessment of moderate hyperthermia effects on the anti-tumor immune response will aid in development of targeted strategies that best combine hyperthermia with other immune manipulating therapies.

MATERIALS/METHODS

To understand the consequences of temperature on carcinogenic phenotypes in vitro, B16-F10 melanoma cells were grown at 37°C or 41°C and biochemical profiles including protein expression were evaluated. Impact of hyperthermia on cell migration and proliferation were also assessed as were changes in the immune milieu including cytokine expression in response to heat. Data obtained was used to define ongoing in vivo experiments in which B16-F10 cells are implanted into C57BL/6 mice, grown to palpable tumors than treated with infrared radiation in combination with either anti-PDL1, anti-PD-1, or IL-15. Future studies based on these initial in vivo studies will explore integration of radiotherapy with hyperthermia and immunotherapy.

RESULTS

B16-F10 cells grown at 41°C decreased cell migration by 70% in 24 hours, and decreased proliferation by 62% at 48 hours and 94% at 72 hours. To assess biochemical orchestrations exemplified by these data, protein expression profiles were evaluated. Expression of pERK and ERK decreased by 86% and 50% and caspase-3 increased by 31% at 41°C. Activation of sphingomyelinase and caspase-3 both rely on caspase-8. Sphingomyelinase activation results in CD95 receptor translocation, leading to cell death initiation in melanoma cells. Cell stress can induce death pathways and the heat shock protein response simultaneously. Of note, Hsp70 has an established role in fostering a tumor specific immune response. Thus, we investigated inducible hsp70 expression. Hsp70 expression increased by 188% at 41°C vs. 37°C. To evaluate the immune milieu, cytokine array data from conditioned media showed that at 41°C, TNFa expression was increased and IL-4 expression was decreased, suggesting a proinflammatory shift in cytokine profiles at hyperthermic temperatures. In support of our data, hyperthermia-induced TNFa apoptotic responses have been reported. In direct relation to clinical practice, we observed that hyperthermic potentiation decreased PDL1 expression in B16-F10 by 35%.

CONCLUSION

Our work to date supports the hypothesis that hyperthermia can enhance immunotherapy via several mechanisms. In vivo study of the ability of hyperthermia to augment immune modulating therapies such as checkpoint blockade and radiation therapy is warranted.

Impact of Quadriceps Tendon Graft Thickness on Electromechanical Delay and Neuromuscular Performance After ACL Reconstruction

Background

Both partial- and full-thickness quadriceps tendon (QT) graft harvests are used for anterior cruciate ligament reconstruction (ACLR).

Purpose

To evaluate the impact of QT graft harvest depth (full or partial thickness) on electromechanical delay (EMD), peak torque (PT), and rate of torque development (RTD) after ACLR.

Study Design

Controlled laboratory study.

Methods

A total of 26 patients who underwent either partial-thickness (n = 14) or full-thickness (n = 12) autograft QT ACLR were recruited between June and November 2021 (>1 year before participation). Patients performed isokinetic knee extension testing with surface electromyography of the quadriceps muscles. Mixed repeated-measures analysis of variance with least significant difference post hoc testing was used to determine significant differences (mean difference [MD] ± SE) or interactions for all variables.

Results

A significant speed×depth interaction was seen for the vastus medialis (P = .005). Pairwise analyses showed significantly longer EMD for the partial-thickness graft than the full-thickness graft (MD ± SE, 19.92 ± 6.33 ms; P = .006). In the partial-thickness graft, the EMD was significantly longer at 90 deg/s versus 180 deg/s (MD ± SE, 19.11 ± 3.95 ms; P < .001) and 300 deg/s (MD ± SE, 16.43 ± 5.30 ms; P = .006). For PT, the full-thickness graft had a significantly lower PT on the operated versus nonoperated side at all speeds (MD ± SE: 90 deg/s, -57.0 ± 10.5 N·m, P < .001; 180 deg/s, -26.0 ± 10.2 N·m, P = .020; 300 deg/s, -20.3 ± 8.9 N·m, P = .034). For RTD, the full-thickness graft showed significantly Slower RTD for the operated versus nonoperated side at all time points (MD ± SD: RTD0-25 (0-25% of the range of motion), -131.3 ± 50.9 N·m/s, P = .018; RTD25-50, -197.0 ± 72.5 N·m/s, P = .014; RTD50-75, -113.3 ± 39.8 N·m/s, P = .013; RTD75-100, -149.4 ± 35.9 N·m/s, P < .001).

Conclusion

Compared with partial-thickness QT, full-thickness QT showed a shorter vastus medialis EMD at higher loading, and therefore greater stiffness, as well as slower RTD and lower PT across all testing speeds.

Clinical Relevance

The impact of full-thickness QT autograft on EMD and neuromuscular performance should be considered for ACLR.

Estimated Dermal Penetration of Tetrachlorvinphos (TCVP) in Humans Based on In Silico Modeling and In Vitro and In Vivo Data

Tetrachlorvinphos (TCVP) is the pesticidal active ingredient in some collars for dogs and cats. The objective of this study was to provide a refined estimate of dermal penetration of TCVP in humans using in silico predictions as well as in vitro and in vivo data. The in vivo dermal absorption of TCVP was previously studied in the rat and shown to be saturable, ranging from 21.7% (10 µg/cm²) down to 3% (1000 µg/cm²) Subsequent in silico predictions were conducted for rats and humans to provide initial evaluations of species and dose-dependent differences in dermal absorption. A definitive comparison of TCVP systemic exposure in rat and human following dermal application was then conducted via a standard in vitro assay. TCVP dose levels of 10, 100, or 1000 μg/cm² were applied to excised rat and human skin mounted in flow-through diffusion cells. The vehicle was 1% hydroxypropylmethylcellulose (HPMC) in water. An additional 5 μg/cm² dose was applied to excised human skin only. The in vitro dermal absorption of TCVP was also assessed from artificial sebum at dose levels of 5, 10, or 100 μg/cm² applied to human skin only. Utilizing the so-called triple pack approach with in vitro and in vivo rat data and in vitro human data, dermal absorption for TCVP was calculated for humans. In silico modeling indicated absorption of TCVP through human skin might be 3- to 4- fold lower than rat skin at all application levels, with a maximum dermal absorption of 9.6% at the lowest exposure of 10 µg/cm², down to 0.1% at 1000 µg/cm². Similar species differences were also found in the definitive in vitro absorption assays. Modeling overestimated TCVP human dermal absorption (9.6%) as compared to excised human skin results (1.7%) for the HPMC vehicle at the lowest exposure (10 µg/cm²), with better agreement at the higher exposures. Conversely, modeling accurately predicted rat dermal absorption (27.9%) as compared to in vivo rat results (21.7%) at the lowest exposure in HPMC, with diminished agreement at the higher exposures. As a first approximation, in silico estimates of dermal absorption are useful; however, these tend to be more variable than in vitro or in vivo measurements. TCVP dermal penetration measured in vitro was lower in 1% HPMC vehicle as compared to artificial sebum. For the 1% HPMC vehicle, in vitro rat dermal absorption was similar to data obtained for in vivo rats, giving confidence in the triple pack approach. In consideration of the triple pack approach, estimated human dermal absorption from 1% HPMC was ≤2%. Based upon excised human skin determinations directly, estimated human dermal absorption of TCVP from artificial sebum was ≤7%.

The Associations Between Quadriceps Tendon Graft Thickness and Isokinetic Performance

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) using the quadriceps tendon is an increasingly popular technique. Both partial-thickness quadriceps tendon (PT-Q) and full-thickness quadriceps tendon (FT-Q) graft depths are employed.

HYPOTHESIS/PURPOSE

This study was designed to assess isokinetic peak torque, average power, and total work during knee extension in patients with FT-Q or PT-Q grafts for ACLR. We hypothesized that both groups would show lower isokinetic values for the operated side, with greater deficits in the FT-Q group than in the PT-Q group.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 26 patients who underwent ACLR with either an FT-Q or PT-Q graft were recruited between June 2021 and November 2021. Patients underwent isokinetic knee extension testing at > 1 year after surgery. Mixed repeated-measures analysis of covariance with least square difference post hoc testing was used to determine significant differences or interactions for all variables.

RESULTS

Peak torque was significantly lower for the operated limb than the nonoperated limb in the FT-Q group (mean difference [MD] ± standard error [SE], -38.6 ± 8.3 Nċm [95% CI, -55.7 to -21.5 Nċm]; P < .001; d = 0.90) but not in the PT-Q group (MD ± SE, -7.3 ± 7.7 Nċm [95% CI, -23.2 to 8.5 Nċm]; P = .348; d = 0.20). Similarly, average power for the operated limb was lower than that for the nonoperated limb in the FT-Q group (MD ± SE, -53.6 ± 13.4 W [95% CI, -81.3 to -26.9 W]; P < .001; d = 0.88) but not in the PT-Q group (MD ± SE, -4.1 ± 12.4 W [95% CI, -29.8 to 21.5 W]; P = .742; d = 0.07), and total work was lower for the operated limb compared with the nonoperated limb in the FT-Q group (MD ± SE, -118.2 ± 27.1 J [95% CI, -174.3 to -62.2 J]; P < .001; d = 0.96) but not in the PT-Q group (MD ± SE, -18.3 ± 25.1 J [95% CI, -70.2 to 33.6 J]; P = .472; d = 0.15).

CONCLUSION

The FT-Q group showed significant deficits in the operated limb compared with the nonoperated limb for all isokinetic variables. In contrast, no significant differences were found between the nonoperated and operated limbs for the PT-Q group.

Assembly and architecture of Escherichia coli divisome proteins FtsA and FtsZ

During Escherichia coli cell division, an intracellular complex of cell division proteins known as the Z-ring assembles at midcell during early division and serves as the site of constriction. While the predominant protein in the Z-ring is the widely conserved tubulin homolog FtsZ, the actin homolog FtsA tethers the Z-ring scaffold to the cytoplasmic membrane by binding to FtsZ. While FtsZ is known to function as a dynamic, polymerized GTPase, the assembly state of its partner, FtsA, and the role of ATP are still unclear. We report that a substitution mutation in the FtsA ATP-binding site impairs ATP hydrolysis, phospholipid vesicle remodeling in vitro, and Z-ring assembly in vivo. We demonstrate by transmission electron microscopy and Förster Resonance Energy Transfer that a truncated FtsA variant, FtsA(ΔMTS) lacking a C-terminal membrane targeting sequence, self assembles into ATP-dependent filaments. These filaments coassemble with FtsZ polymers but are destabilized by unassembled FtsZ. These findings suggest a model wherein ATP binding drives FtsA polymerization and membrane remodeling at the lipid surface, and FtsA polymerization is coregulated with FtsZ polymerization. We conclude that the coordinated assembly of FtsZ and FtsA polymers may serve as a key checkpoint in division that triggers cell wall synthesis and division progression.

Degradation of MinD oscillator complexes by Escherichia coli ClpXP

MinD is a cell division ATPase in Escherichia coli that oscillates from pole to pole and regulates the spatial position of the cell division machinery. Together with MinC and MinE, the Min system restricts assembly of the FtsZ-ring to midcell, oscillating between the opposite ends of the cell and preventing FtsZ-ring misassembly at the poles. Here, we show that the ATP-dependent bacterial proteasome complex ClpXP degrades MinD in reconstituted degradation reactions in vitro and in vivo through direct recognition of the MinD N-terminal region. MinD degradation is enhanced during stationary phase, suggesting that ClpXP regulates levels of MinD in cells that are not actively dividing. ClpXP is a major regulator of growth phase–dependent proteins, and these results suggest that MinD levels are also controlled during stationary phase. In vitro, MinC and MinD are known to coassemble into linear polymers; therefore, we monitored copolymers assembled in vitro after incubation with ClpXP and observed that ClpXP promotes rapid MinCD copolymer destabilization and direct MinD degradation by ClpXP. The N terminus of MinD, including residue Arg 3, which is near the ATP-binding site in sequence, is critical for degradation by ClpXP. Together, these results demonstrate that ClpXP degradation modifies conformational assemblies of MinD in vitro and depresses Min function in vivo during periods of reduced proliferation.

Longer small bowel segments are resected in emergency surgery for ileocaecal Crohn's disease with a higher ileostomy and complication rate

BACKGROUND

Repeated intestinal resections may have disabling consequences in patients with Crohn's disease even in the absence of short bowel syndrome. Our aim was to evaluate the length of resected small bowel in patients undergoing elective and emergency surgery for ileocolic Crohn's disease.

METHODS

A prospective observational study was conducted on patients undergoing surgery for ileocolonic Crohn's disease in a single colorectal centre from May 2010 to April 2018. The following patients were included: (1) patients with first presentation of ileocaecal Crohn's disease undergoing elective surgery; (2) patients with ileocaecal Crohn's disease undergoing emergency surgery; (3) patients with recurrent Crohn's disease of the distal ileum undergoing elective surgery. The primary outcomes were length of resected small bowel and the ileostomy rate. Operating time, complications and readmissions within 30 days were the secondary outcomes.

RESULTS

One hundred and sixty-eight patients were included: 87 patients in the elective primary surgery group, 50 patients in the emergency surgery group and 31 in the elective redo surgery group. Eleven patients (22%) in the emergency surgery group had an ileostomy compared to 10 (11.5%) in the elective surgery group (p < 0.0001). In the emergency surgery group the median length of the resected small bowel was 10 cm longer than into the group having elective surgery for primary Crohn's disease.

CONCLUSIONS

Patients undergoing emergency surgery for Crohn's disease have a higher rate of stoma formation and 30-day complications. Laparoscopic surgery in the emergency setting has a higher conversion rate and involves resection of longer segments of small bowel.

The differential actions of clozapine and other antipsychotic drugs on the translocation of dopamine D2 receptors to the cell surface

Most clinically available antipsychotic drugs (APDs) bind dopamine D2 receptors (D2R) at therapeutic concentrations, and it is thought that they suppress psychotic symptoms by serving as competitive antagonists of dopamine at D2R. Here, we present data that demonstrate that APDs act independently of dopamine at an intracellular pool of D2R to enhance transport of D2R to the cell surface and suggest that APDs can act as pharmacological chaperones at D2R. Among the first- and second-generation APDs that we tested, clozapine exhibited the lowest efficacy for translocating D2R to the cell surface. Thus, our observations could provide a cellular explanation for some of the distinct therapeutic characteristics of clozapine in schizophrenia. They also suggest that differential intracellular actions of APDs at their common G protein-coupled receptor (GPCR) target, D2R, could contribute to differences in their clinical profiles.

Laparoscopic Redo Ileocolic Resection for Crohn's Disease in Patients with Previous Multiple Laparotomies

PURPOSES:

Over 80% of patients with primary ileocolic Crohn's disease have a surgical resection within 10 years of diagnosis, and 40%-50% of them need further surgery within 15 years. Laparoscopic surgery can be challenging due to a thickened mesentery and the potential for fistulas, abscesses, and phlegmons. Aim of this study is to analyze the short-term outcomes of laparoscopic redo ileocolic resections for Crohn's disease in patients with previous multiple laparotomies.

METHODS:

All patients undergoing laparoscopic surgery for ileocolic Crohn's disease from March 2006 to February 2017 were prospectively evaluated. Short term outcomes of laparoscopic ileocolic resection were compared between patients with previous multiple major surgeries and recurrent Crohn's disease, and patients undergoing surgery for the first presentation of Crohn's disease and no history of previous surgery. Conversion rate and 30-day morbidity were the primary outcomes. Reoperations, readmissions, operating time and length of stay were the secondary outcomes.

RESULTS:

29 patients with recurrent Crohn's disease and previous multiple laparotomies were included: the number of laparotomies these patients previously underwent was 2 in 19 cases (65.5%), 3 in 9 (31%), and 4 in 1 (3.5%). In total, 90 patients with no history of any previous abdominal surgery, who underwent laparoscopic ileocecal resection for Crohn's disease, represented the control group. No differences were found in morbidity and conversion rate. Operating time was longer in patients with history of previous abdominal surgery.

CONCLUSION:

Laparoscopic redo ileocolic resection for Crohn's disease is feasible and safe in patients with previous multiple laparotomies at the expense of longer operating time.

FtsA reshapes membrane architecture and remodels the Z-ring in Escherichia coli

Cell division in prokaryotes initiates with assembly of the Z-ring at midcell, which, in Escherichia coli, is tethered to the inner leaflet of the cytoplasmic membrane through a direct interaction with FtsA, a widely conserved actin homolog. The Z-ring is comprised of polymers of tubulin-like FtsZ and has been suggested to provide the force for constriction. Here, we demonstrate that FtsA exerts force on membranes causing redistribution of membrane architecture, robustly hydrolyzes ATP and directly engages FtsZ polymers in a reconstituted system. Phospholipid reorganization by FtsA occurs rapidly and is mediated by insertion of a C-terminal membrane targeting sequence (MTS) into the bilayer and further promoted by a nucleotide-dependent conformational change relayed to the MTS. FtsA also recruits FtsZ to phospholipid vesicles via a direct interaction with the FtsZ C-terminus and regulates FtsZ assembly kinetics. These results implicate the actin homolog FtsA in establishment of a Z-ring scaffold, while directly remodeling the membrane and provide mechanistic insight into localized cell wall remodeling, invagination and constriction at the onset of division.

The Protein Chaperone ClpX Targets Native and Non-native Aggregated Substrates for Remodeling, Disassembly, and Degradation with ClpP

ClpX is a member of the Clp/Hsp100 family of ATP-dependent chaperones and partners with ClpP, a compartmentalized protease, to degrade protein substrates bearing specific recognition signals. ClpX targets specific proteins for degradation directly or with substrate-specific adaptor proteins. Native substrates of ClpXP include proteins that form large oligomeric assemblies, such as MuA, FtsZ, and Dps in Escherichia coli. To remodel large oligomeric substrates, ClpX utilizes multivalent targeting strategies and discriminates between assembled and unassembled substrate conformations. Although ClpX and ClpP are known to associate with protein aggregates in E. coli, a potential role for ClpXP in disaggregation remains poorly characterized. Here, we discuss strategies utilized by ClpX to recognize native and non-native protein aggregates and the mechanisms by which ClpX alone, and with ClpP, remodels the conformations of various aggregates. We show that ClpX promotes the disassembly and reactivation of aggregated Gfp-ssrA through specific substrate remodeling. In the presence of ClpP, ClpX promotes disassembly and degradation of aggregated substrates bearing specific ClpX recognition signals, including heat-aggregated Gfp-ssrA, as well as polymeric and heat-aggregated FtsZ, which is a native ClpXP substrate in E. coli. Finally, we show that ClpX is present in insoluble aggregates and prevents the accumulation of thermal FtsZ aggregates in vivo, suggesting that ClpXP participates in the management of aggregates bearing ClpX recognition signals.

Proteolysis-Dependent Remodeling of the Tubulin Homolog FtsZ at the Division Septum in Escherichia coli

During bacterial cell division a dynamic protein structure called the Z-ring assembles at the septum. The major protein in the Z-ring in Escherichia coli is FtsZ, a tubulin homolog that polymerizes with GTP. FtsZ is degraded by the two-component ATP-dependent protease ClpXP. Two regions of FtsZ, located outside of the polymerization domain in the unstructured linker and at the C-terminus, are important for specific recognition and degradation by ClpXP. We engineered a synthetic substrate containing green fluorescent protein (Gfp) fused to an extended FtsZ C-terminal tail (residues 317–383), including the unstructured linker and the C-terminal conserved region, but not the polymerization domain, and showed that it is sufficient to target a non-native substrate for degradation in vitro. To determine if FtsZ degradation regulates Z-ring assembly during division, we expressed a full length Gfp-FtsZ fusion protein in wild type and clp deficient strains and monitored fluorescent Z-rings. In cells deleted for clpX or clpP, or cells expressing protease-defective mutant protein ClpP(S97A), Z-rings appear normal; however, after photobleaching a region of the Z-ring, fluorescence recovers ~70% more slowly in cells without functional ClpXP than in wild type cells. Gfp-FtsZ(R379E), which is defective for degradation by ClpXP, also assembles into Z-rings that recover fluorescence ~2-fold more slowly than Z-rings containing Gfp-FtsZ. In vitro, ClpXP cooperatively degrades and disassembles FtsZ polymers. These results demonstrate that ClpXP is a regulator of Z-ring dynamics and that the regulation is proteolysis-dependent. Our results further show that FtsZ-interacting proteins in E. coli fine-tune Z-ring dynamics.

The bacterial cell division regulators MinD and MinC form polymers in the presence of nucleotide

The Min system of proteins, consisting of MinC, MinD and MinE, is essential for normal cell division in Escherichia coli. MinC forms a polar gradient to restrict placement of the division septum to midcell. MinC localization occurs through a direct interaction with MinD, a membrane-associating Par-like ATPase. MinE stimulates ATP hydrolysis by MinD, thereby releasing MinD from the membrane. Here, we show that MinD forms polymers with MinC and ATP without the addition of phospholipids. The topological regulator MinE induces disassembly of MinCD polymers. Two MinD mutant proteins, MinD(K11A) and MinD(ΔMTS15), are unable to form polymers with MinC.

Vulnerability and social justice as factors in emergent U.S. nanotechnology risk perceptions

As an emerging domain of risk research, nanotechnologies engender novel research questions, including how new technologies are encountered given different framing and contextual detail. Using data from a recent U.S. national survey of perceived risks (N= 1,100), risk versus benefit framings and the specific social positions from which people encounter or perceive new technologies are explored. Results indicate that vulnerability and attitudes toward environmental justice significantly influenced risk perceptions of nanotechnology as a broad class, while controlling for demographic and affective factors. Comparative analyses of different examples of nanotechnology applications demonstrated heightened ambivalence across acceptability when risk versus benefit information was provided with application descriptions (described in short vignettes as compared to the general category "nanotechnology," absent of risk or benefit information). The acceptability of these nano-specific vignettes varied significantly in only some cases given indexes of vulnerability and attitudes toward environmental justice. However, experimental narrative analyses, using longer, more comprehensive descriptive passages, show how assessments of risks and benefits are tied to the systematically manipulated psychometric qualities of the application (its invasiveness and controllability), risk messaging from scientists, and the social implications of the technology with regard to justice. The article concludes with discussion of these findings for risk perception research and public policy related to nanotechnology and possibly other emerging technologies.

Can we predict the spreading of a two-liquid system from the spreading of the corresponding liquid-air systems?

We present new data obtained from the spreading of a series of oil droplets, on top of a hydrophobic grafted silicon substrate, in air and immersed in water. We follow the contact angle and radius dynamics of hexane, dodecane, hexadecane, dibutyl phthalate, and squalane from the first milliseconds to approximately 1 s. Analysis of the images allows us to make several hundred contact angle and droplet radius measurements with great accuracy. The G-Dyna (Seveno et al. Langmuir 2010, 25, 13034) software is then used to fit the data with one of the wetting theories, the molecular-kinetic theory (MKT) (Blake et al. J. Colloid Interface Sci.1969, 30, 421), which takes into account the dissipation at the three-phase zone at the contact line. This theory allows us to extract the coefficient of friction of the contact line, which expresses the relationship between the driving force, that is, the unbalanced Young force, and the contact-line velocity V. It is first shown that the MKT is appropriate to describe the experimental data and then that the contact-line friction is a linear function of the viscosity as theoretically predicted. This is checked for oil-air and oil-water systems. A linear relation between the contact-line friction measured in oil-water systems and the contact-line frictions of the parent single liquid system seems plausible. To the best of our knowledge, this is the first trial to establish a link between the dynamics of wetting in liquid-liquid and in liquid-air systems.

Dynamics of wetting revisited

We present new spreading-drop data obtained over four orders of time and apply our new analysis tool G-Dyna to demonstrate the specific range over which the various models of dynamic wetting would seem to apply for our experimental system. We follow the contact angle and radius dynamics of four liquids on the smooth silica surface of silicon wafers or PET from the first milliseconds to several seconds. Analysis of the images allows us to make several hundred contact angle and droplet radius measurements with great accuracy. The G-Dyna software is then used to fit the data to the relevant theory (hydrodynamic, molecular-kinetic theory, Petrov and De Ruijter combined models, and Shikhmurzaev's formula). The distributions, correlations, and average values of the free parameters are analyzed and it is shown that for the systems studied even with very good data and a robust fitting procedure, it may be difficult to make reliable claims as to the model which best describes results for a given system. This conclusions also suggests that claims based on smaller data sets and less stringent fitting procedures should be treated with caution.

Anticipating the perceived risk of nanotechnologies

Understanding emerging trends in public perceptions of nanomaterials is critically important for those who regulate risks. A number of surveys have explored public perceptions of their risks and benefits. In this paper we meta-analyse these surveys to assess the extent to which the following four hypotheses derived from previous studies of new technologies might be said to be valid for nanotechnologies: risk aversion will prevail over benefit appreciation; an increase in knowledge will not result in reduced aversion to risks; judgements will be malleable and subject to persuasion given risk-centric information; and contextual, psychometric and attitudinal predictors of perceived risk from prior studies can help anticipate future perceptions of nanotechnologies. We find that half the public has at least some familiarity with nanotechnology, and those who perceive greater benefits outnumber those who perceive greater risks by 3 to 1. However, a large minority of those surveyed (44%) is unsure, suggesting that risk judgements are highly malleable. Nanotechnology risk perceptions also appear to contradict some long-standing findings. In particular, unfamiliarity with nanotechnology is, contrary to expectations, not strongly associated with risk aversion and reduced 'knowledge deficits' are correlated with positive perceptions in this early and controversy-free period. Psychometric variables, trust and affect continue to drive risk perceptions in this new context, although the influence of both trust and affect is mediated, even reversed, by demographic and cultural variables. Given the potential malleability of perceptions, novel methods for understanding future public responses to nanotechnologies will need to be developed.

Nanotoxicology: characterizing the scientific literature, 2000-2007

Understanding the toxicity of nanomaterials and nano-enabled products is important for human and environmental health and safety as well as public acceptance. Assessing the state of knowledge about nanotoxicology is an important step in promoting comprehensive understanding of the health and environmental implications of these new materials. To this end, we employed bibliometric techniques to characterize the prevalence and distribution of the current scientific literature. We found that the nano-toxicological literature is dispersed across a range of disciplines and sub-fields; focused on in vitro testing; often does not specify an exposure pathway; and tends to emphasize acute toxicity and mortality rather than chronic exposure and morbidity. Finally, there is very little research on consumer products, particularly on their environmental fate, and most research is on the toxicity of basic nanomaterials. The implications for toxicologists, regulators and social scientists studying nanotechnology and society are discussed.

Ligand-receptor interactions in complex media: a new type of biosensors for the detection of coagulation factor VIII

Detection of receptor-ligand interaction in complex media remains a challenging issue. We report experimental results demonstrating the specific detection of the coagulation factor VIII in the presence of a large excess of other proteins using the new BIA-ATR technology based on attenuated total reflection Fourier transform infrared spectroscopy. The principle of the detection is related to the ability of factor VIII molecules to bind to lipid membranes containing at least 8% phosphatidylserine. Several therapeutic concentrates of factor VIII were analyzed and the binding of the coagulation factor was monitored as a function of time. We show that a non-specific adsorption of stabilizing agents (typically, von Willebrand factor and human serum albumin) may be avoided by controlling the geometry of the ATR element. A linear response of the sensors as a function of the factor VIII concentration is described for different lipid membrane compositions.

Superhydrophobic surfaces from various polypropylenes

Superhydrophobic surfaces were prepared from solutions of isotactic polypropylenes of various molecular weights using soft chemistry. Varying the conditions of the experiments (polymer concentration and initial amount of the coated solution) allowed us to optimize the superhydrophobic behavior of the polymer film. Results show that decreasing the concentration and/or film thicknesses decreases the probability to get superhydrophobicity for all polypropylenes tested. Measurement and analysis of advancing and receding contact angles as well as estimation of surface homogeneity were performed. Similar results were obtained with syndio- as well as atactic polypropylenes.

Contact-line friction of liquid drops on self-assembled monolayers: chain-length effects

The static and dynamic wetting properties of self-assembled alkanethiol monolayers of increasing chain length were studied. The molecular-kinetic theory of wetting was used to interpret the dynamic contact angle data and evaluate the contact-line friction on the microscopic scale. Although the surfaces had a similar static wettability, the coefficient of contact-line friction zeta0 increased linearly with alkyl chain length. This result supports the hypothesis of energy dissipation due to a local deformation of the nanometer-thick layer at the contact line.

Biochemical interaction analysis on ATR devices: a wet chemistry approach for surface functionalization

A new generic device suitable for the investigation of ligand-receptor interactions is presented. In particular, the research focused on optical waveguides constituted by an attenuated total internal reflection (ATR) element, transparent in the infrared and whose surfaces were activated in view of covalently binding a receptor. Silicon and germanium ATR elements were considered. The original method is based on the grafting of bifunctional spacer molecules directly at the surface of the germanium crystal, avoiding the deposition of an intermediate metal layer. The grafting of these binding molecules (under their N-hydroxysuccinimidyl ester forms) was performed either by wet chemistry or by photochemistry. The functionalized surfaces, which allow the binding of molecules bearing peripherical NH2 groups, were successfully used, e.g., for the detection of proteins (streptavidin) or of small molecules (biotin). In the latter case, the biotin was readily detected for concentrations as low as 10(-12) M.

Postnatal depression, eating, exercise, and vomiting before and during pregnancy

OBJECTIVE

To examine the postnatal distress and the eating, exercise, and weight losing behavior of women before and during pregnancy.

METHOD

The subjects were healthy women who had given birth to a singleton healthy baby in the week before the study. They were drawn from two consecutive series of mothers of babies whose birth weights were either < or =2,500 g or >2,500 g. A total of 181 women were interviewed using a standardized interview modified for pregnancy and related behaviors. They also completed the Edinburgh Postnatal Distress Questionnaire.

RESULTS

Regression analysis produced a final model containing variables that made a unique contribution to predicting the level of distress of women in the week following childbirth. The model accounted for 25% of the variance and included four variables that were associated with greater distress: fear of weight gain before and during pregnancy, being distracted by thoughts of food during pregnancy, being afraid of gaining more weight than the pregnancy would explain, and vomiting more frequently during the first 3-4 months of pregnancy. A fifth variable accounted for less distress, that is, participating in low-intensity exercise for reasons of shape and weight during months 3-4 of pregnancy. Other variables associated with distress only in the preliminary analysis were maternal age, binge eating, and vomiting before pregnancy. The most distressed mothers were suffering from an eating disorder at the time of pregnancy. The binge and/or purge type of eating disorder was associated with more distress than a food restriction type.

DISCUSSION

Postnatal distress is associated with body weight and shape concerns, with disordered eating before and during pregnancy, and with vomiting during pregnancy. The protective role of low-intensity exercise during early pregnancy needs to be explored. Women with eating disorders should be considered at risk for postnatal problems.

Self-Cleaving-Ribozyme-Mediated Reduction of βAPP in Human Rhabdomyosarcoma Cells

A self-cleaving hammerhead ribozyme targeted to codon 47 in beta-amyloid precursor protein (betaAPP) mRNA was cloned as a eucaryotic transcription cassette into the 3' UTR of enhanced green fluorescence protein (EGFP) mRNA, producing a C-terminal fusion mRNA. CMV promotor-driven vectors bearing this construct or a mutationally inactive ribozyme construct were transiently transfected into human embryonic rhabdomyosarcoma (A-204) cells and their effects studied. Ribozyme self-cleavage in vivo was demonstrated by Northern blotting and the site of self-cleavage was delineated using site-specific deoxyoligonucleotide probes and primer extension arrest. Using this ribozyme reporter we demonstrated that ribozyme expression correlated with lower betaAPP levels in the transfected cells. Control studies with the inactive ribozyme construct showed that both ribozyme cleavage and antisense mechanisms combined to produce the observed effect. Furthermore, production of truncated EGFP mRNA via ribozyme self-cleavage reduced EGFP-reporter expression compared to full-length EGFP control mRNAs, indicating that truncation affects the translatability of the reporter. This occurred because of a slight decrease in the stability of the fusion mRNA. The results of these studies suggest that self-cleaving ribozyme vectors may be an effective means of delivering and visualizing the expression of small active ribozymes in vivo.

In vivo ribozyme targeting of betaAPP+ mRNAs

In Alzheimer's disease (AD) and Down's syndrome (DS) patients, posttranscriptional alterations of sequences encoded by exon 9 and exon 10 of the beta-amyloid precursor protein (betaAPP) mRNA result in mutant proteins (betaAPP+) that colocalize with neurofibrillary tangles and senile plaques. These aberrant messages may contribute to the development of sporadic or late-onset Alzheimer's disease; thus, eliminating them or attenuating their expression could significantly benefit AD patients. In the present work, self-cleaving hammerhead ribozymes targeted to betaAPP exon 9 (Rz9) and betaAPP+ mutant exon 10 (Rz10) were examined for their ability to distinguish between betaAPP and betaAPP+ mRNA. In transiently transfected A-204 cells, quantitative confocal fluorescence microscopy showed that Rz9 preferentially lowered endogenous betaAPP. In contrast, in transient cotransfection experiments with betaAPP+ mRNAs containing a wild-type exon 9 and mutant exon 10 (betaAPP-9/betaAPP-10+1), or a mutant exon 9 and wild-type exon 10 (betaAPP-9+1/betaAPP-10) we found that Rz9 and Rz10 preferentially reduced betaAPP+ -mutant exon 10 mRNA in a concentration and a ribozyme-dependent manner.

RNAs that interact with the fragile X syndrome RNA binding protein FMRP

The Fragile X protein FMRP is an RNA binding protein whose targets are not well known; yet, these RNAs may play an integral role in the disease's etiology. Using a biotinylated-FMRP affinity resin, we isolated RNAs from the parietal cortex of a normal adult that bound FMRP. These RNAs were amplified by differential display (DDRT-PCR) and cloned and their identities determined. Nine candidate RNAs were isolated; five RNAs, including FMR1 mRNA, encoded known proteins. Four others were novel. The specificity of binding was demonstrated for each candidate RNA. The domains required for binding a subset of the RNAs were delineated using FMRP truncation mutant proteins and it was shown that only the KH2 domain was required for binding. Binding occurred independently of homoribopolymer binding to the C-terminal arginine-glycine-rich region (RGG box), suggesting that FMRP may bind multiple RNAs simultaneously.

Haemodynamic responses to extubation after cardiac surgery with and without continued sedation

We studied the haemodynamic response to cessation of mechanical ventilation and removal of the tracheal tube in 84 patients after coronary artery bypass grafting. Patients were sedated on the ICU with propofol 1-3 mg kg-1 h-1, and randomly allocated to extubation while awake or while still sedated. Systolic and diastolic blood pressures and heart rate increased significantly faster in the awake group as mechanical ventilation was stopped; systolic blood pressure 6.1 (3.0) vs 0.7 (1.8) mm Hg min-1, diastolic blood pressure 2.1 (1.6) vs 0.2 (0.9) mm Hg min-1, heart rate 2.1 (1.7) vs 0.2 (0.5) beats min-2; P < 0.01 in each case. Treatment was required for systolic hypertension during discontinuation of mechanical ventilation in 20 patients (53%) in the awake group and in three patients (7.5%) in the sedated group (P < 0.001). No patient in the sedated group had any new ischaemic ECG changes. Significant new ST segment changes did not occur in the sedated group but were present in five patients in the awake group (P = 0.013), one of whom suffered a perioperative myocardial infarction. Removal of the tracheal tube while patients are still sedated after coronary artery bypass grafting is safe, and reduces the incidences of haemodynamic disturbance and myocardial ischaemia during extubation.

A comparison of purging and nonpurging eating-disordered outpatients: mediating effects of weight and general psychopathology

OBJECTIVES

The present study compared purging and nonpurging eating-disordered outpatients on key behavioral and psychological features of their disorder. It also investigated the possible mediating effects of current level of depression, anxiety or general psychopathology, and current weight on differences between purgers and nonpurgers.

METHOD

Seventy-seven patients from an outpatient eating disorder clinic who purged were compared to 48 clinic patients who did not purge on measures of eating behavior disturbances and specific psychopathology while controlling for weight, level of depression, anxiety, and general distress.

RESULTS

Purgers reported significantly more eating behavior disturbance and higher scores on measures of specific psychopathology than the nonpurgers. These differences were unrelated to current weight, level of anxiety, or general distress. However, severity of depression did moderate some of the difference between the groups.

CONCLUSION

These data provide further support for the proposition that purging is a distinctive clinical marker in all types of eating-disordered patients.

Eating behavior and pregnancy outcome

The association between clinical eating disorders, maternal body weight, shape, and eating concerns, and the birth of low-birth-weight infants (LBW; less than 2500 g) was investigated using a retrospective case-control study. Eighty-eight women delivering LBW infants were interviewed and then divided into two groups--those delivering term, small-for-gestational-age infants (SGA; 37 or more completed weeks, n = 34) and those delivering premature infants (less than 37 completed weeks, n = 54). There were 86 reference women (CTRL) matched for age, parity, and health insurance status, who delivered babies with birth weights greater than 2500 g. In the week postpartum, women delivering term SGA, premature (PREM), and CTRL infants were interviewed using a semistructured interview. One section of this interview included a modified version of the Eating Disorder Examination (EDE), which retrospectively generated, over the previous 12 months, diagnosis of an eating disorder and maternal "normative" weight and shape concerns. In the 3 months before pregnancy, 32% of SGA women, 9% PREM women, and 5% of reference women were diagnosed as having a clinical eating disorder. Women with a past history of an eating disorder had no greater risk of delivering a low-birth-weight infant. Women delivering SGA infants, reported elevated eating disorder psychopathology postdelivery (Eating Disorders Inventory, EDI) and more disturbances in eating behavior before and during pregnancy. Unique predictors for delivery of a LBW term SGA infant were: low maternal prepregnancy body weight, smoking, low maternal weekly weight gain, and elevated EDI (Bulimia subscale). Unique predictors for delivery of a LBW premature infant were: lower maternal occupational status, vomiting in pregnancy, and lower dietary restraint. Women with disordered eating were shown to be at greater risk of delivering term SGA infants. Predictors of term growth retardation are partly determined by maternal behavior.

Preoperative 5-FU, low-dose leucovorin, and radiation therapy for locally advanced and unresectable rectal cancer

PURPOSE

We report the local control and survival of two Phase I dose escalation trials of combined preoperative 5-fluorouracil (5-FU), low-dose leucovorin (LV), and radiation therapy followed by postoperative LV/5-FU for the treatment of patients with locally advanced and unresectable rectal cancer.

METHODS AND MATERIALS

A total of 36 patients (30 primary and 6 recurrent) received two monthly cycles of LV/5-FU (bolus daily x 5). Radiation therapy (50.40 Gy) began on day 1 in the 25 patients who received concurrent treatment and on day 8 in the 11 patients who received sequential treatment. Postoperatively, patients received a median of four monthly cycles of LV/5-FU.

RESULTS

The resectability rate with negative margins was 97%. The complete response rate was 11% pathologic and 14% clinical for a total of 25%. The 4-year actuarial disease-free survival was 67% and the overall survival was 76%. The crude local failure rate was 14% and the 4-year actuarial local failure rate was 30%. Crude local failure was lower in the four patients who had a pathologic complete response (0%) compared with those who either did not have a pathologic complete response (16%) or who had a clinical complete response (20%).

CONCLUSION

Our preliminary data with the low-dose LV regimen reveal encouraging downstaging, local control, and survival rates. Additional follow-up is needed to determine the 5-year results. The benefit of downstaging on local control is greatest in patients who achieve a pathologic complete response.

Preoperative 5-fluorouracil, low-dose leucovorin, and concurrent radiation therapy for rectal cancer

BACKGROUND

A Phase I trial was performed to determine the maximum tolerated dose of concurrent preoperative radiation therapy (5040 cGy) and 2 cycles (bolus daily times 5) of 5-fluorouracil (5-FU) and low-dose leucovorin (LV) (20 mg/m2), followed by surgery and 10 cycles of postoperative 5-FU/LV in patients with primary or recurrent rectal cancer.

METHODS

Twenty-four patients were entered into the study. Preoperatively, the initial dose of 5-FU was 325 mg/m2. 5-FU was escalated 50 mg/m2, while the dose of LV and radiation therapy remained constant. Chemotherapy and radiation began concurrently on day 1. The postoperative chemotherapy was not dose escalated; 5-FU, 425 mg/m2, and LV, 20 mg/m2. The median follow-up was 10 months (range, 4-19 months).

RESULTS

The resectability rate with negative margins in the 23 patients who underwent surgery was 100%. One patient refused surgery. The pathologic complete response rate was 13% (3 of 23). An additional four patients had negative nodes and a microscopic foci of tumor in the bowel wall. Therefore, the total clinical complete response rate was 30% (7 of 23). The maximum tolerated dose of 5-FU for the preoperative combined modality segment was 375 mg/m2; therefore, the recommended Phase II dose level is 325 mg/m2. The incidence of Grade 3+ toxicity for the 22 patients treated at the recommended 5-FU dose level (325 mg/m2) during the preoperative combined modality segment was as follows: diarrhea, 14%; erythema, 5%; hematologic, 10%; and total, 18%. The median nadir counts were leukocyte count, 3.7 (range, 1.5-5.9); hemoglobin count, 12.2 (range, 10.2-14.3); and platelet count (times 1000), 165 (range, 92-237).

CONCLUSIONS

With this regimen, the recommended doses of chemotherapy in the combined modality segment are slightly higher than those recommended in arm 2 of the Intergroup postoperative adjuvant rectal trial 0114. This regimen will serve both as the preoperative arm of the Intergroup randomized trial of preoperative versus postoperative combined modality therapy for resectable rectal cancer (INT R9401) as well as the basis for the combined modality segment of NSABP RO-3.

Preoperative 5-fluorouracil, low-dose leucovorin, and concurrent radiation therapy for rectal cancer

BACKGROUND

A Phase I trial was performed to determine the maximum tolerated dose of concurrent preoperative radiation therapy (5040 cGy) and 2 cycles (bolus daily times 5) of 5-fluorouracil (5-FU) and low-dose leucovorin (LV) (20 mg/m2), followed by surgery and 10 cycles of postoperative 5-FU/LV in patients with primary or recurrent rectal cancer.

METHODS

Twenty-four patients were entered into the study. Preoperatively, the initial dose of 5-FU was 325 mg/m2. 5-FU was escalated 50 mg/m2, while the dose of LV and radiation therapy remained constant. Chemotherapy and radiation began concurrently on day 1. The postoperative chemotherapy was not dose escalated; 5-FU, 425 mg/m2, and LV, 20 mg/m2. The median follow-up was 10 months (range, 4-19 months).

RESULTS

The resectability rate with negative margins in the 23 patients who underwent surgery was 100%. One patient refused surgery. The pathologic complete response rate was 13% (3 of 23). An additional four patients had negative nodes and a microscopic foci of tumor in the bowel wall. Therefore, the total clinical complete response rate was 30% (7 of 23). The maximum tolerated dose of 5-FU for the preoperative combined modality segment was 375 mg/m2; therefore, the recommended Phase II dose level is 325 mg/m2. The incidence of Grade 3+ toxicity for the 22 patients treated at the recommended 5-FU dose level (325 mg/m2) during the preoperative combined modality segment was as follows: diarrhea, 14%; erythema, 5%; hematologic, 10%; and total, 18%. The median nadir counts were leukocyte count, 3.7 (range, 1.5-5.9); hemoglobin count, 12.2 (range, 10.2-14.3); and platelet count (times 1000), 165 (range, 92-237).

CONCLUSIONS

With this regimen, the recommended doses of chemotherapy in the combined modality segment are slightly higher than those recommended in arm 2 of the Intergroup postoperative adjuvant rectal trial 0114. This regimen will serve both as the preoperative arm of the Intergroup randomized trial of preoperative versus postoperative combined modality therapy for resectable rectal cancer (INT R9401) as well as the basis for the combined modality segment of NSABP RO-3.

The pony as an animal model for vascular implants

This study evaluated the pony as a potentially suitable model for vascular implant research. Healthy, conditioned ponies were randomly assigned to one of three groups: group I, carotid artery autografts (n = 6); group II, e-PTFE carotid interpositional grafts (n = 5); and group III, e-PTFE carotid interpositional grafts plus aspirin (10 mg/kg) and dipyridamole (3.5 mg/kg) drug administration. It was found that autografts remained patent longest (mean = 396.2 days; grafts were still patent at time of writing) followed by group III grafts (157.5 days), with group II grafts remaining patent for the shortest duration (61.1 days), (p less than 0.01). Patency was determined using two-dimensional real-time ultrasonography with Doppler velocimetry and/or arteriography. It was demonstrated that the pony's response to antithrombotic drugs was consistent and comparable to that in other animal models, both with respect to platelet function and affect on patency rate. The combination of the ease of surgical manipulation, drug administration, and platelet function testing, the comparable size of the pony and its heart and blood vessels to that of an adult human, the long life span of ponies, and the patency results of this study have demonstrated that the pony is a valuable animal model for vascular research.

Platelet function testing in the pony

Platelet isolation techniques and platelet function were evaluated in 35 adult ponies. Platelet recovery from whole blood was consistent and the preparation of platelet rich plasma was facilitated by an enhanced erythrocyte sedimentation rate. All platelet samples aggregated in response to 10 microM ADP. However, concentrations of ADP as high as 100 microM did not elicit significant 14C-serotonin release. Collagen induced irreversible platelet aggregation and 14C-serotonin release in all samples. The threshold dose for collagen in most ponies was 1.5 micrograms. Arachidonic acid (500 microM) failed to induce irreversible platelet aggregation or 14C-serotonin release in any of the samples evaluated. Pony platelets were nonresponsive to epinephrine (5.5 microM).

An ionotropic phase transition in phosphatidylcholine: cation and anion cooperativity

Evidence is presented for cooperative interaction between cations and anions specifically bound to dimyristoylphosphatidylcholine (DMPC). The cooperativity is with regard to an ion-induced (ionotropic) phase transition for the lipid and is signalled by a change in the luminescence from bound Tb3+. The intrinsic binding of Tb3+ to DMPC was determined from equilibrium dialysis experiments, using conventional methods to correct for electrostatic contributions. Preliminary results demonstrate great potential for infrared spectroscopy as a means to relate these Tb3+ luminescence studies to experiments involving less tractable cations. This work provides insight into the role of bound ions in modifying lateral phase behavior in phospholipid membranes.

Accuracy of PET RCBF measurements: effect of time shift between blood and brain radioactivity curves

Analytic expressions were derived for estimating the error in PET RCBF measurements associated with the time lag between brain and blood radioactivity following bolus H2(15)O injection and during non-steady-state CO15O inhalation. This lag time reflects the physiological difference in arrival times of 15O activity at brain and radial arterial sampling site as well as the experimentally introduced resistance to flow offered by the arterial catheter/stopcock assembly. Multiple measurements of this time lag ranged between 1 and 10 s. For non-steady-state CO15O PET measurements, estimated errors in RCBF ranged from 0.02 to 30% for delays of 2-8 s and scan lengths of 30-180 s. In the range 20-100 ml min-1 per 100 g, variations in RCBF only marginally affected these errors. Errors increased with longer delays but decreased sharply with scan durations greater than 60 s. For 30-180 s scans, even larger errors are associated with the H2(15)O injection technique (peak blood activity at 10 s): 1-60% for delays of 2-8 s. A 'slow' bolus peaking at 20 s decreased the error by 40%. For the H2(15)O method it is essential to estimate the time shift to within 2 s if accurate flow measurements (error less than 5%) are to be obtained from 40-60 s scans.

Quantitative CT assessment of furosemide- and mannitol-induced changes in brain water content

We studied the effects of two commonly employed antiedema agents, mannitol and furosemide, on CT brain density in eight patients with primary and metastatic brain tumors. Noncontrast CTs were performed before and after IV furosemide or IV mannitol, and serial blood samples were analyzed for osmolality. Computer-generated frequency histograms of CT numbers from "before-and-after" brain slices were using quantile-quantile (QQ) plots and the Kruskal-Wallis statistic. After IV mannitol, there was a progressive increase in CT brain density, which corresponded to an upward shift in the QQ plot over the range 0 to 70 Hounsfield units. The differences between baseline and posttreatment histograms for mannitol patients were significantly different from controls, and maximum differences coincided with peak serum osmolality. No statistically significant effects were observed in the furosemide group despite maximal diuresis. The relative magnitude of the quantitative changes observed after mannitol and furosemide administration are consistent with anticipated changes in brain water content.

Mass spectrometric measurement of end-tidal xenon concentration for clinical stable xenon/computerized tomography cerebral blood flow studies

We have demonstrated the feasibility of using a compact dedicated mass spectrometer to monitor end-tidal xenon concentration in human subjects during stable xenon computerized tomography measurements of regional cerebral blood flow. End-tidal carbon dioxide concentration is monitored simultaneously and noninvasively without degrading the dynamic response to xenon. For clinical regional cerebral blood flow studies we employed a Nuclide 3-60-G Sectorr mass spectrometer with a 3 in radius, 60 degrees magnetic sector and a variable (0-5000 V) ion accelerating potential. The required high vacuum (10(-7) Torr) was achieved and maintained by means of a turbomolecular pump. A needlemetering valve was incorporated into an anesthesia mask connector, and exhaled gases were transported to the mass spectrometer via a 6 ft length of Teflon tubing (1/16 in i.d.). Molecular flow conditions between the sample and analysis chambers were provided by use of a gold foil leak (0.0005 in. hole). At an inlet pressure of 400 m Torr (achieved by means of the needle valve), the inlet system was characterized by a gas transport lag-time of 1.3 s and a rise-time constant of 85 ms. Xenon (doubly charged ion: m/z 68) and carbon dioxide (doubly charged ion: m/z 22) were monitored alternately at 75 ms intervals. Our experience with mass spectrometry has demonstrated the feasibility of using a compact dedicated instrument for accurately and non-invasively monitoring end-tidal xenon concentration in a clinical setting.

An inexpensive video patient repositioning system for use with transmission and emission computed tomographs

We have designed and constructed a portable video system from commercially available components (total cost $5,000) to facilitate accurate patient repositioning for sequential computed tomographic (CT) and positron emission tomographic studies and for therapeutic radiation therapy. The repositioning accuracy of the video system, employed in conjunction with a Delta-Scan 2020 CT scanner, was compared qualitatively (skull phantom and patient subjects) and quantitatively (precision cone phantom) with that of a GE 8800 CT scanner equipped with ScoutView and crossed Gammex lasers (SVL system). Although the SVL and video systems both facilitated accurate repositioning, the video system proved slightly superior. With experience, Z-axis repositioning accuracy of better than 1 mm could be achieved.