Cardiovascular Disease Burden and Outcomes Among American Indian and Alaska Native Medicare Beneficiaries

Importance

American Indian and Alaska Native persons face significant health disparities; however, data regarding the burden of cardiovascular disease in the current era is limited.

Objective

To determine the incidence and prevalence of cardiovascular disease, the burden of comorbid conditions, including cardiovascular disease risk factors, and associated mortality among American Indian and Alaska Native patients with Medicare insurance.

Design, Setting, and Participants

This was a population-based cohort study conducted from January 2015 to December 2019 using Medicare administrative data. Participants included American Indian and Alaska Native Medicare beneficiaries 65 years and older enrolled in both Medicare part A and B fee-for-service Medicare. Statistical analyses were performed from November 2022 to April 2023.

Main Outcomes and Measures

The annual incidence, prevalence, and mortality associated with coronary artery disease (CAD), heart failure (HF), atrial fibrillation/flutter (AF), and cerebrovascular disease (stroke or transient ischemic attack [TIA]).

Results

Among 220 598 American Indian and Alaska Native Medicare beneficiaries, the median (IQR) age was 72.5 (68.5-79.0) years, 127 402 were female (57.8%), 78 438 (38.8%) came from communities in the most economically distressed quintile in the Distressed Communities Index. In the cohort, 44.8% of patients (98 833) were diagnosed with diabetes, 61.3% (135 124) were diagnosed with hyperlipidemia, and 72.2% (159 365) were diagnosed with hypertension during the study period. The prevalence of CAD was 38.6% (61 125 patients) in 2015 and 36.7% (68 130 patients) in 2019 (P < .001). The incidence of acute myocardial infarction increased from 6.9 per 1000 person-years in 2015 to 7.7 per 1000 patient-years in 2019 (percentage change, 4.79%; P < .001). The prevalence of HF was 22.9% (36 288 patients) in 2015 and 21.4% (39 857 patients) in 2019 (P < .001). The incidence of HF increased from 26.1 per 1000 person-years in 2015 to 27.0 per 1000 person-years in 2019 (percentage change, 4.08%; P < .001). AF had a stable prevalence of 9% during the study period (2015: 9.4% [14 899 patients] vs 2019: 9.3% [25 175 patients]). The incidence of stroke or TIA decreased slightly throughout the study period (12.7 per 1000 person-years in 2015 and 12.1 per 1000 person-years in 2019; percentage change, 5.08; P = .004). Fifty percent of patients (110 244) had at least 1 severe cardiovascular condition (CAD, HF, AF, or cerebrovascular disease), and the overall mortality rate for the cohort was 19.8% (43 589 patients).

Conclusions and Relevance

In this large cohort study of American Indian and Alaska Native patients with Medicare insurance in the US, results suggest a significant burden of cardiovascular disease and cardiometabolic risk factors. These results highlight the critical need for future efforts to prioritize the cardiovascular health of this population.

214 The Role of Water-Soluble Contrast Enemas in Assessing Anastomoses Prior to Ileostomy Reversal, and Their Influence on Patient Outcomes

Aim

Water-soluble contrast enemas (WSCE) are routinely performed to check anastomotic integrity and patency in patients who have undergone a low anterior resection and loop ileostomy formation, in preparation for subsequent ileostomy reversal. However, no specific guideline exists in this regard. Our aim was to evaluate whether WSCE influence management and patient outcomes.

Method

WSCE examinations performed between January 2019 to March 2021 were retrieved. Radiology reports, discharge summaries, and clinic letters were retrospectively collected from prospectively maintained data to determine outcomes.

Results

Over the 24-month period, we identified 63 patients who underwent a WSCE following an anterior resection. Seven had positive radiological leaks (11%), and six of these seven underwent further investigations, then either proceeded to a successful reversal (3) or are awaiting surgery (3).

Additionally, WSCE identified 10 strictures (16%). Again, due to these findings, they underwent additional investigations before proceeding to interventions (ileostomy reversal, endoscopic dilatation, or resection of stenosed anastomosis).

In total 30 patients (48%) underwent an ileostomy reversal. Only one (2%) was not successful due to a small bowel leak, not related to the low anastomosis.

Conclusions

This study demonstrates a positive WSCE result impacts subsequent investigations or interventions required. A positive result (leak or stricture) was never a contra-indication for reversal, and none of the positive results had significant postoperative complications. The only unsuccessful reversal was not related to the low anastomosis and had a normal WSCE. The exact investigations required, and their timeframe remains unclear, and we question whether radiological or endoluminal examinations should be routinely performed.

1113 Surgical Innovators or Spin Doctors: Reporting of Expectations for Robotic Gastrointestinal Surgery

Introduction

The use of robotics in gastrointestinal surgery is an increasingly popular area of surgical innovation. Despite uncertainty regarding clinical benefits, gastrointestinal surgery centres continue to introduce robotic services. This may be motivated by perceived benefits, in lieu of substantial empirical benefits. We aimed to summarise the expected advantages and disadvantages of robotic techniques in gastrointestinal surgery, as reported by study authors.

Method

A systematic review was undertaken by the trainee led RoboSurg Collaborative. Searches were conducted on of Embase, Medline, the Cochrane Library and Web of Science. Articles were double screened by abstract, then full text. All primary studies reporting outcomes following robotic cholecystectomy or oesophagectomy were included. Reports of expected benefits and disadvantages or robotic techniques were extracted verbatim, and summarised using descriptive statistics.

Results

We included 192 studies. An expected benefit was reported in 161 (84%). Of those, 127 (79%) expected robotics to have an intra-operative advantage, such as reduced operative time, improved dexterity and improved visualisation. Post-operative benefits, such as reduced recovery time and shorter length of hospital stay, were expected in 72 (45%). Expected disadvantages were reported in 96 (50%) of the included studies. Of those, 74 (77%) expected robotics to have intra-operative disadvantages such as increased operative times and lack of tactile feedback. Increased cost was another commonly expected limitation.

Conclusions

Study authors reported perceived benefits more frequently than disadvantages. Perceived benefits were more commonly advantageous to the surgeon rather than the patient. There were directly conflicting perceptions of how robotic techniques affect operative times.

1165 Reporting Patient Selection in Robotic Cholecystectomy: Less than IDEAL? A Systematic Review

Introduction

Laparoscopic cholecystectomy is the gold standard definitive treatment option for benign biliary disease. There has been increasing interest in novel robotic surgical techniques; robotic cholecystectomy (RC) represents the most recent innovation in the management of gallstones. The IDEAL Collaboration has provided guidance for the rigorous and comprehensive reporting of surgical innovations, despite this, transparency in patient selection has been limited. We aimed to assess the reporting of patient selection in studies reporting RC.

Method

A collaborative, systematic review was conducted in accordance with the PRISMA guidance to identify all published studies reporting RC. Study specific inclusion and exclusion criteria were detailed in a protocol.

Results

Searches identified 1425 abstracts; 90 papers were included for data extraction. Inclusion criteria were reported in 38 (42%) studies. The most frequently cited were age (20%), aetiology (20%), presence of symptoms (16%) and comorbidities (10%). Forty-nine (54%) studies reported exclusion criteria. Numerous and variably reported exclusion criteria were reported; acute cholecystitis (26%), previous abdominal surgery (25%), comorbidity (17%), pregnancy (13%), common bile duct stones (13%) and pancreatitis (10%) among others. Seven reported no exclusion criteria. Three reported numbers of patients who declined RC.

Conclusions

Patient selection criteria were inconsistently reported and when present lacked standardisation. Concern persists around patients being “cherry picked” for inclusion in studies reporting innovative robotic surgical procedures, making interpretation and applicability of results impossible. Standardised inclusion criteria are needed to enable greater transparency and reproducibility to ensure the safe adoption of new technologies into clinical practice.

1232 Trust-Wide Assessment of Delirium in Post-Operative Elective Surgery

Aim

Delirium is an acute change in cognition and associated with adverse patient outcomes. The incidence of post-operative delirium after elective non-cardiac surgery is unknown. We aimed to assess the incidence of post-operative delirium in this group and the effect on patient outcomes.

Method

Patients aged 65 and over who underwent elective non-cardiac surgery were identified on post-operative day three. Delirium screening was performed in real time using the validated 4-AT assessment tool. A retrospective review of the patients’ preoperative and perioperative record was conducted to collect demographics and identify risk factors for delirium. Outcome data was collected at 30 days. Patients with a positive delirium score (&gt;4) underwent a more in-depth assessment and managing teams given a delirium management pack.

Results

75 (39 male) consecutive patients were screened over a period of 4 months. Median age 77 years and 18% had frailty assessed as “vulnerable”. The majority of patients (37.3%) underwent thoracic surgery, followed by hepatobiliary (17.3%), gynaecological (17.3%), colorectal (12%), maxillofacial (9.3%) and ENT (4%). 5.3% (4) of patients had a positive 4-AT screen. No patients had a formal delirium screen or diagnosis in the initial 48 hours. The median length of stay for patients with a positive screen was 8.5 days (IQR 7.5-12) compared to 8 days (IQR 5-13) for patients with a negative screen.

Conclusions

Reassuringly, rate of post-operative delirium following elective operations in our Trust are low (5%). Larger numbers of patients are required to assess the impact this has on patient outcomes and identify correlation with risk factors.

Impact of surgical complications on the operating surgeon

AIM

The involvement of surgeons in major adverse outcomes can have a negative impact on their personal and professional lives, as well as on patient outcomes. Healthcare professionals involved in such incidents have been referred to as 'second victims'. We designed an online survey to study the impact of operative complications on surgeons' professional and personal lives.

METHOD

An online survey of general, gastrointestinal, hepato-pancreato-biliary and vascular surgeons was conducted using the Twitter feed of the Association of Coloproctology of Great Britain and Ireland, the Association of Surgeons of Great Britain and Ireland and the European Society of Coloproctology over an 8-week period.

RESULTS

Questionnaires were completed by 82 participants. Ninety-one per cent of respondents were consultant surgeons, 37% with more than 15 years' experience. Eighty-three per cent were colorectal surgeons. The majority of surgeons (95%) reported that their practice had been affected as a result of serious complications and 54% suggested that it had had a negative impact on their family life. Fifty-five per cent of respondents mentioned lack of support in their institution for healthcare professionals involved in adverse outcomes and an existing blame culture. Suggestions for improvement included mentoring (41%), counselling (38%), openness (66%), peer support groups (52%) and human factors training (32%).

CONCLUSION

This survey highlights that the majority of surgeons involved in serious complications are adversely affected. Those involved in the running of surgical services need to improve support for surgeons in the aftermath of such events.

Incidence and risk factors for alopecia in survivors of critical illness: A multi-centre observational study

PURPOSE

To investigate the incidence, nature and risk factors for patient-reported alopecia in survivors of critical illness.

MATERIALS AND METHODS

A multi-centre, mixed methods observational study in the intensive care units (ICU) of ten hospitals in Wales. All patients with an ICU stay of 5 days or more, able to give consent were included. Demographic variables and risk factors were collected. A pre-designed survey was completed at three months post-ICU discharge. Statistical analysis included numbers and percentages (categorical variables) and medians and interquartile ranges (continuous variables). Comparisons between patients with and without alopecia were made using Fisher's Exact test (categorical variables) and Mann Whitney U test (continuous variables). Multivariate logistic regression analysis was used to determine the risk factors for alopecia.

RESULTS

The survey was completed by 123 patients with alopecia reported in 44 (36%) patients. The only risk factor for alopecia on analysis was sepsis / septic shock (p < .001; OR: 5.1, 95%CI: 2.1-12.4).

CONCLUSIONS

Limited research exists examining the incidence, nature and risk factors for patient-reported alopecia in adult survivors of critical illness. The results of this study highlight the need to discuss the potential for alopecia with survivors of critical illness, who had sepsis / septic shock.

Spline modelling electron insert factors using routine measurements

There are many methods available to predict electron output factors; however, many centres still measure the factors for each irregular electron field. Creating an electron output factor prediction model that approaches measurement accuracy--but uses already available data and is simple to implement--would be advantageous in the clinical setting. This work presents an empirical spline model for output factor prediction that requires only the measured factors for arbitrary insert shapes. Equivalent ellipses of the insert shapes are determined and then parameterised by width and ratio of perimeter to area. This takes into account changes in lateral scatter, bremsstrahlung produced in the insert material, and scatter from the edge of the insert. Agreement between prediction and measurement for the 12 MeV validation data had an uncertainty of 0.4% (1SD). The maximum recorded deviation between measurement and prediction over the range of energies was 1.0%. The validation methodology showed that one may expect an approximate uncertainty of 0.5% (1SD) when as little as eight data points are used. The level of accuracy combined with the ease with which this model can be generated demonstrates its suitability for clinical use. Implementation of this method is freely available for download at https://github.com/SimonBiggs/electronfactors.

Falls exercise interventions and reduced falls rate: always in the patient's interest?

Falls are a leading cause of mortality and morbidity in older adults. Physical, psychological and social consequences include injury, fall-related fear and loss of self-efficacy. In turn, these may result in decreased physical activity, reduced functional capacity, and increased risk of institutionalisation. Falls prevention exercise programmes (FPEP) are now widespread within the National Health Service, often part of multifactorial interventions, and are designed to minimise impairments that impact physical function, such as strength and balance. Assessment of the clinical efficacy of FPEPs has therefore focused on the measurement of physical function and rate of falls. Whilst important, this approach may be too narrow to capture the highly variable and multidimensional responses that individuals make to a fall and to a FPEP. We argue that the current focus may miss a paradoxical lack of or even deleterious impact on quality of life, despite a reduction in physical performance-related falls risk. We draw upon the Selective Optimisation and Compensation (SOC) model, developed by Paul and Margret Baltes, to explore how this paradox may be a result of the coping strategies adopted by individuals in response to a fall.

Interstitial high dose rate (HDR) brachytherapy for early stage breast cancer

10551

Background: External Beam Radiation Therapy (EBRT) has been the standard of care for breast conservation radiation therapy. Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares favorably to EBRT in selected patients. Methods: Patients with Tis, T1, and T2 tumors measuring ≤ 3 cm, negative surgical margins, and negative axillary lymph nodes were judged to be candidates for Interstitial Implant. Results: Between 2000 and 2006, 112 patients underwent Interstitial HDR Implant under Stereotactic Mammographic guidance with conscious sedation and local anesthesia. Conscious sedation consisted of Morphine and Versed. Local anesthesia was given with a mixture of 1% Lidocaine, 0.25% Marcaine, 1:100,000 Epinephrine, and 4% Sodium Bicarbonate neutralizing solution. The implants were placed using a Template with from 3 to 6 planes, and 8 to 43 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation Treatment planning was performed using CT Scanning. Treatment volumes ranged from 25 cm3 to 359 cm3. The breast implant volume received 3400 cGy in 10 fractions via HDR prescribed to the Planning Target Volume, given BID over 5 days. The procedure was well tolerated. No patient required hospital admission. With a median follow-up 36 months (range 6–60 months), local recurrence occurred in 2.7% (3/112). Cosmetic results were good to excellent in 85.7% (96/112) of the patients. Wound healing complications developed in 7.1% (8/112). Three of these patients had received anthracycline based Chemotherapy. The other five had large (> 200 cm3) implant volumes and catheter spacing of 1.5 cm. Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis. Conclusions: With median 36 month follow-up, Breast Conservation radiation therapy utilizing Interstitial HDR Implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatment with anthracycline based Chemotherapy and large (> 200 cm3) implant volumes appear to be relative contraindications to Interstitial HDR Implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications.

No significant financial relationships to disclose.

The influence of chain length and electrolyte on the adsorption kinetics of cationic surfactants at the silica–aqueous solution interface

The equilibrium and kinetic aspects of the adsorption of alkyltrimethylammonium surfactants at the silica-aqueous solution interface have been investigated using optical reflectometry. The effect of added electrolyte, the length of the hydrocarbon chain, and of the counter- and co-ions has been elucidated. Increasing the length of the surfactant hydrocarbon chain results in the adsorption isotherm being displaced to lower concentrations. The adsorption kinetics indicate that above the cmc micelles are adsorbing directly to the surface and that as the chain length increases the hydrophobicity of the surfactant has a greater influence on the adsoption kinetics. While the addition of 10 mM KBr increases the CTAB maximal surface excess, there is no corresponding increase for the addition of 10 mM KCl to the CTAC system. This is attributed to the decreased binding efficiency of the chloride ion relative to the bromide ion. Variations in the co-ion species (Li, Na, K) have little effect on the adsorption rate and surface excess of CTAC up to a bulk electrolyte concentration of 10 mM. However, the rate of adsorption is increased in the presence of electrolyte. Slow secondary adsorption is seen over a range of concentrations for CTAC in the absence of electrolyte and importantly in the presence of LiCl; the origin of this slow adsorption is attributed to a structural barrier to adsorption.

Mechanism of cationic surfactant adsorption at the solid-aqueous interface

Until recently, the rapid time scales associated with the formation of an adsorbed surfactant layer at the solid-aqueous interface has prevented accurate investigation of adsorption kinetics. This has led to the mechanism of surfactant adsorption being inferred from thermodynamic data. These explanations have been further hampered by a poor knowledge of the equilibrium adsorbed surfactant morphology, with the structure often misinterpreted as simple monolayers or bilayers, rather than the discrete surface aggregates that are present in many surfactant-substrate systems. This review aims to link accepted equilibrium data with more recent kinetic and structural information in order to describe the adsorption process for ionic surfactants. Traditional equilibrium data, such as adsorption isotherms obtained from depletion approaches, and the most popular methods by which these data are interpreted are examined. This is followed by a description of the evidence for discrete aggregation on the substrate, and the morphology of these aggregates. Information gained using techniques such as atomic force microscopy, fluorescence quenching and neutron reflectivity is then reviewed. With this knowledge, the kinetic data obtained from relatively new techniques with high temporal resolution, such as ellipsometry and optical reflectometry, are examined. On this basis the likely mechanisms of adsorption are proposed.

Viscosity effect on the structural compactness of latex flocs formed under weak depletion attractions

Dilute aqueous dispersions of colloidal polystyrene latex spheres were flocculated by adding a nonadsorbing polymer sample, poly(acrylic acid). The structural compactness of the flocs thus formed was characterized in terms of their mass fractal dimension using the small-angle static light scattering technique. It was found that with low poly(acrylic acid) concentrations and thus weak depletion attraction forces, the dispersion medium viscosity had a marked effect on the floc structure. An increase in the viscosity led to formation of denser flocs. This was revealed in three sets of depletion flocculation experiments: (a) adjusting the background electrolyte concentration at a fixed level of poly(acrylic acid), (b) using water and 30% (w/w) glycerol as the respective solvents, and (c) inducing latex flocculation with two poly(acrylic acids) of different molecular weights at the respective critical polyacid concentrations. Direct force measurements were made with atomic force microscopy to isolate the influence of viscosity on floc structure from that of interparticle interaction energies. We conclude that the formation of denser flocs with increasing medium viscosity can be attributed to the reduced diffusivity of particles in the solution. The latter resulted in an enhanced rate of floc restructuring (through relaxation of attached particles) relative to floc growth.

Microscopic and macroscopic aspects of stick-slip motion in granular shear

An annular shear cell has been used to investigate a number of factors known to influence stick-slip motion in an assembly of near monosized, spherical glass beads. In this paper, both the sample shear stress and volumetric strain were recorded, allowing new insights into the possible mechanics of stick-slip motion in a granular body. Rather than the commonly presented mechanism of sample dilation and fluidization accompanying the slip events, in the material studied here, sample dilation occurred during the preslip deformations of the granular body, while the slip event was accompanied by assembly contraction. Drive velocity and applied normal pressure were both found to influence the magnitude of the stick-slip spikes in a manner analogous to previous studies of stick-slip in assemblies of confined, near-spherical lubricant systems. Finally, atmospheric relative humidity was found to have a marked effect on the magnitude of the stick-slip motion. To investigate this mechanism more fully, the atomic force microscopy was employed to measure the particle-particle interaction forces as a function of atmospheric relative humidity. A water meniscus was found to form under all humidities, from less than 5% to greater than 95%. However, its influence on the adhesive forces varied by an order of magnitude. While most previous studies of stick-slip phenomena have attempted to remove atmospheric humidity as a variable, here we present a useful link between the role of relative humidity on particle-particle interaction forces and the macroscopic response of the granular assembly.

Assessing the health impact of age-specific housing

It has been claimed that 'retirement communities', defined in this instance as voluntary communities of older people living in shared, purpose-built housing, combine the best attributes of residential and community living. Subjective health status may thereby be improved through a culture in which independence and autonomy are actively promoted. Concern has also been raised that age-segregated communities of this sort might produce 'ghettos' of increasing dependency and service demand. This study, conducted over a 12-month time period, found that when compared to older people living in the local neighbourhood, the retirement community population maintained their physical and mental health (utilising measures including the SF36, Life Satisfaction Index, and 18 semantic differentials). Investigation of these findings indicated that peer support and safety/security, and 'autonomy with inclusion' were key factors in maintaining health status.

A Foucauldian analysis of old age and the power of social welfare

It is argued that the question of social welfare is a key, if often overlooked, component in the construction of power relations and identities in later life that can take its place next to debates on bioethics and consumer lifestyle. Foucault's (1977) claim, that identities are kept in place through the deployment of integrated systems of power and knowledge and a routine operation of surveillance and assessment, is critically examined in this context. Trends in social welfare in the United Kingdom are used as a case example that sheds light on wider contemporary issues associated with old age. Finally, implications for the creation of particular narratives about later life are discussed and grounded through Foucault's (1988) notion of "technologies of self."

Microscopic and macroscopic effects of surface lubricant films in granular shear

Experiments were conducted to investigate the link between particle-particle interaction forces and the bulk properties of granular shear using an idealized system of near-spherical, monosized glass beads. The atomic force microscopy colloidal probe technique was employed to investigate the adhesion and friction between a single bead and a second glass surface, while the annular shear cell was used to measure the shear properties of the bulk granular material. A covalently bound monomolecular film of aliphatic chains was introduced to alter the tribological interactions between the particles. The atomic force microscope was used to measure the reduction in the particle-particle surface forces resulting from the addition of the boundary lubricant, while the shear cell showed that the effect of the lubricant film was to reduce the coefficient of internal friction and the dilation during shear. This is an experimental study to provide quantitative data linking particle-particle interaction forces and the shear properties of a granular body.

Lateral Force Microscopy Study of the Friction between Silica Surfaces

The friction between a single silica glass sphere and a flat silica glass surface has been investigated using lateral force microscopy. Two types of silica surface were investigated, one fully hydroxylated and the other partially dehydroxlated. These samples have markedly different wetting properties and are known as hydrophilic and hydrophobic silica, respectively. The lateral friction force as a function of applied normal load has been collected for five different-sized spheres for both surface types. Analysis of the friction versus load data indicates that the hydrophilic surfaces have a molecularly smooth contact. For the hydrophobic surfaces, it is not clear whether the friction-load response is caused by a smooth or an asperity-dominated contact zone. Copyright 2000 Academic Press.

Force Calibration in Lateral Force Microscopy

An analysis of the contact mechanics and the forces of interaction in lateral force microscopy measurements is presented. This analysis allows for a new method of interpretation of the frictional forces, the lateral contact stiffness, and the contact shear strength. The technique was developed for the interpretation of frictional data obtained with colloidal probes, although results are presented which illustrate its ability to interpret measurements recorded with both colloidal probes and standard atomic force microscopy tips. The technique is found to compensate for the variations in the contact geometry, giving repeatable results for probes of different sizes. A critical review of other techniques which have been employed to interpret the frictional force in lateral force microscopy is also presented. Copyright 2000 Academic Press.

Ultrasonic initiation of polystyrene latex synthesis

Polystyrene latex samples have been synthesised from an oil-in-water (o/w) emulsion of the monomer using ultrasonic irradiation as the initiation source. No added chemical initiators were used in any of the reactions. The free radicals formed from the cavitation process under the action of the ultrasound are sufficient to initiate the polymerisation. In the current study, the effects of varying the input intensity of the ultrasound were investigated. A marked increase in the monomer conversion rate as a function of time was seen as the power was increased. Despite this increase in conversion rate, the increasing intensity did not affect the resultant latex particle sizes. In all cases, the particle diameters at the conclusion of a polymerisation were seen to be in the range of 40 to 50 nm. The effects of changing the concentration of surfactant in the polymerisation medium and of changing the temperature were also probed. Increases in both were seen to lead to an increased rate of conversion at a fixed input intensity. Again, the particle diameters were invariant as a function of changing conditions. The small particle sizes and high conversion rates are thought to be due to a continuous nucleation process that is caused by the scavenging of free radicals throughout the polymerisation by freshly formed small oil droplets.

Modification of a Commercial Atomic Force Microscope for Nanorheological Experiments: Adsorbed Polymer Layers

The atomic force microscope (AFM) has previously been applied to the measurement of surface forces (including adhesion and friction) and to the investigation of material properties, such as hardness. Here we describe the modification of a commercial AFM that enables the "stiffness" of interaction between surfaces to be measured concurrently with the surface forces. The stiffness is described by the rheological phase difference between the response of the AFM tip to a driving oscillation of the substrate. We present the interaction between silica surfaces bearing adsorbed polymer, however, the principles could be applied to a wide variety of materials including biological samples.

Butyl Acrylate/Vinyl Acetate Copolymer Latex Synthesis Using Ultrasound As an Initiator

The polymerization of oil-in-water (o/w) emulsions of monomeric species has been performed at 30&deg;C (&plusmn;5&deg;C) under ultrasonic irradiation, in the absence of any added chemical initiators. Emulsions of butyl acrylate and vinyl acetate as well as emulsified mixtures of the two monomers have been reacted in this way. In all cases, the radicals formed as a result of the ultrasonic cavitation were sufficient to cause polymerization. Stable blue-white or white dispersions of polymer latex particles were obtained. The kinetics of the copolymerization process were monitored. The data obtained here show that the polymerization rate depends strongly upon the monomer concentration dissolved in the aqueous phase and on its vapor pressure. The more volatile of the monomers examined, vinyl acetate, was seen to have a markedly lower polymerization rate at equivalent monomer concentrations when compared to the butyl acrylate. This was attributed to monomer evaporation into the cavities formed by the ultrasound, causing a dampening of the cavitation process and hence a lower radical density. Data of particle sizes and polymer molecular weights for the latex samples support this hypothesis.

The Direct Measurement of the Forces of Interaction between a Colloid Particle and an Oil Droplet

An atomic force microscope was used to measure the forces between a silica sphere (diameter 10 &mu;m) and a n-decane droplet (diameter 0.3 mm) in water. Force-distance profiles showed a weak attraction and adhesion due to van der Waals forces. When the anionic surfactant sodium dodecyl sulfate was added, there was electrostatic repulsion at all separations due to the adsorption of the anionic surfactant at the oil-water interface, and no adhesion of the sphere to the oil droplet was observed upon retraction. Fitting the repulsive curves to the nonlinear Poisson-Boltzmann equation for heterogeneous surfaces yielded surface potentials on the oil surface which were consistently lower than those values found from electrokinetic experiments on oil drops under similar conditions. The measured Debye lengths were also found to be significantly different from those calculated from the surfactant and electrolyte conditions employed. Possible reasons for the discrepancies are outlined.

ZG-1494 alpha, a novel platelet-activating factor acetyltransferase inhibitor from Penicillium rubrum, isolation, structure elucidation andbiological activity

A novel inhibitor of platelet-activating factor (PAF) acetyltransferase, an essential enzyme in the remodeling pathway of platelet-activating factor synthesis, was identified by a high throughout screen of natural product extracts of microbial origin. The compound, ZG-1494 alpha, was isolated from an ethyl acetate extract of a culture broth of Penicillium rubrum through bioassay guided fractionation. The structure of ZG-1494 alpha was determined by spectroscopic methods. A key feature of the structure, which is relatively rare among natural products, is the 5-hydroxy-3-pyrrolin-2-one moiety. A 13C-13C INADEQUATE was utilized to unambiguously determine the regiochemistry of this molecule.

Expression cloning and signaling properties of the rat glucagon receptor

Glucagon and the glucagon receptor are a primary source of control over blood glucose concentrations and are especially important to studies of diabetes in which the loss of control over blood glucose concentrations clinically defines the disease. A complementary DNA clone for the glucagon receptor was isolated by an expression cloning strategy, and the receptor protein was expressed in several kidney cell lines. The cloned receptor bound glucagon and caused an increase in the intracellular concentration of adenosine 3', 5'-monophosphate (cAMP). The cloned glucagon receptor also transduced a signal that led to an increased concentration of intracellular calcium. The glucagon receptor is similar to the calcitonin and parathyroid hormone receptors. It can transduce signals leading to the accumulation of two different second messengers, cAMP and calcium.

Interpretations of nonstress tests by obstetric nurses

Five 20-minute nonstress-test strips were mailed to 1,000 members of NAACOG--the organization for obstetric, gynecologic, and neonatal nurses. The individuals were selected systematically from NAACOG's 10 districts. For the 412 (41%) respondents, at least 84% of the answers concurred on each of the five strips. The majority opinion was taken to be the correct answer. Concurrence with the majority was independent of clinical experience, clinical training, and the extent of present nonstress-test responsibilities. The same five strips were interpreted by obstetricians in a previously reported survey. On a two-point, reactive-nonreactive scale, the sample of obstetric nurses' degree of agreement differed significantly from the sample of physicians' degree of agreement (92 versus 98%) on only one strip.

Multiplication of tobacco mosaic virus in tobacco leaf disks is inhibited by (2'-5) oligoadenylate

The oligonucleotide (2'-5') oligoadenylate that is induced in interferon-treated animal cells protects plant tissue from infection by the tobacco mosaic virus. This inhibition of virus multiplication was obtained at concentrations comparable to those affecting protein synthesis and antiviral activities in animal cells. After treatment with (2'-5') oligoadenylate, the multiplicability of tobacco mosaic virus was reduced by 80 to 90 percent as measured by enzyme-linked immunosorbent assay. These results, along with the observation that human interferon protects tobacco tissue from infection by tobacco mosaic virus, indicate that plants and animals may have a common pathway for virus resistance.