Will all youth answer sexual orientation and gender-related survey questions? An analysis of missingness in a large U.S. survey of adolescents and young adults

Some researchers and clinicians may feel hesitant to assess sexual orientation and gender-related characteristics in youth surveys because they are unsure if youth will respond to these questions or are concerned the questions will cause discomfort or offense. This can result in missed opportunities to identify LGBTQ+ youth and address health inequities among this population. The aim of this study was to examine the prevalence and sociodemographic patterns of missingness among survey questions assessing current sexual orientation, gender identity and expression (SOGIE), and past change in sexual orientation (sexual fluidity) among a diverse sample of U.S. youth. Participants (N = 4,245, ages 14-25 years; 95% cisgender, 70% straight/heterosexual, 53% youth of color), recruited from an online survey panel, completed the Wave 1 survey of the longitudinal Sexual Orientation Fluidity in Youth (SO*FLY) Study in 2021. Current SOGIE, past sexual fluidity, and sociodemographic characteristics were assessed for missingness. Overall, 95.7% of participants had no missing questions, 3.8% were missing one question, and 0.5% were missing ≥ 2 questions. Past sexual fluidity and assigned sex were most commonly missing. Sociodemographic differences between participants who skipped the SOGIE questions and the rest of the sample were minimal. Missingness for the examined items was low and similar across sociodemographic characteristics, suggesting that almost all youth are willing to respond to survey questions about SOGIE. SOGIE and sexual fluidity items should be included in surveys and clinical assessments of youth to inform clinical care, policy-making, interventions, and resource development to improve the health of all youth. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The Development and Use of a New Visual Tool (REVISIT) to Support Participant Recall: Web-Based Interview Study Among Older Adults

BACKGROUND

Qualitative health services research often relies on semistructured or in-depth interviews to develop a deeper understanding of patient experiences, motivations, and perspectives. The quality of data gathered is contingent upon a patient's recall capacity; yet, studies have shown that recall of medical information is low. Threats to generating rich and detailed interview data may be more prevalent when interviewing older adults.

OBJECTIVE

We developed and studied the feasibility of using a tool, Remembering Healthcare Encounters Visually and Interactively (REVISIT), which has been created to aid the recall of a specific telemedicine encounter to provide health services research teams with a visual tool, to improve qualitative interviews with older adults.

METHODS

The REVISIT visual appointment summary was developed to facilitate web-based interviews with our participants as part of an evaluation of a geriatric telemedicine program. Our primary aims were to aid participant recall, maintain focus on the index visit, and establish a shared understanding of the visit between participants and interviewers. The authors' experiences and observations developing REVISIT and using it during videoconference interviews (N=16) were systematically documented and synthesized. We discuss these experiences with REVISIT and suggest considerations for broader implementation and future research to expand upon this preliminary work.

RESULTS

REVISIT enhanced the interview process by providing a focus and catalyst for discussion and supporting rapport-building with participants. REVISIT appeared to support older patients' and caregivers' recollection of a clinical visit, helping them to share additional details about their experience. REVISIT was difficult to read for some participants, however, and could not be used for phone interviews.

CONCLUSIONS

REVISIT is a promising tool to enhance the quality of data collected during interviews with older, rural adults and caregivers about a health care encounter. This novel tool may aid recall of health care experiences for those groups for whom it may be more challenging to collect accurate, rich qualitative data (eg, those with cognitive impairment or complex medical care), allowing health services research to include more diverse patient experiences.

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.

Real-world evaluation of a two-step testing algorithm for Clostridioides difficile infection

During the 4 years after implementation of the 2-step Clostridioides difficile infection (CDI) testing algorithm, 70% to 78% of patients with suspected CDI and a positive nucleic acid amplification test but a negative toxin test (NAAT+/TOX-) received CDI treatment. Overall, 73% of NAAT+/TOX- patients were classified as having probable or possible CDI.

Patient and provider perspectives of personal health record use: a multisite qualitative study in HIV care settings

Use of tethered personal health records (PHRs) can streamline care, reduce unnecessary care utilization, and improve health outcomes for people living with human immunodeficiency virus (HIV). Providers play a role in influencing patients' decision to adopt and use PHRs. To explore patient and provider acceptance and use of PHRs in an HIV care setting. We used a qualitative study design guided by the Unified Theory of Acceptance and Use of Technology. Participants included providers of HIV care, patients living with HIV, and PHR coordinating and support staff in the Veterans Health Administration (VA). Interviews were analyzed using directed content analysis. We interviewed providers (n = 41), patients living with HIV (n = 60), and PHR coordinating and support staff (n = 16) at six VA Medical Centers between June and December 2019. Providers perceived PHR use could enhance care continuity, appointment efficiency, and patient engagement. Yet, some expressed concerns that patient PHR use would increase provider workload and detract from clinical care. Concerns about poor PHR interoperability with existing clinical tools further eroded acceptance and use of PHRs. PHR use can enhance care for patients with HIV and other complex, chronic conditions. Negative provider attitudes toward PHRs may impact providers' encouragement of use among patients, consequently limiting patient uptake. Multipronged interventions at the individual, institutional, and system level are needed to enhance PHR engagement among both providers and patients.

Development and Validation of Quality Measures for Testosterone Prescribing

Context

Accurate measures to assess appropriateness of testosterone prescribing are needed to improve prescribing practices.

Objective

This work aimed to develop and validate quality measures around the initiation and monitoring of testosterone prescribing.

Methods

This retrospective cohort study comprised a national cohort of male patients receiving care in the Veterans Health Administration who initiated testosterone during January or February 2020. Using laboratory data and diagnostic codes, we developed 9 initiation and 7 monitoring measures. These were based on the current Endocrine Society guidelines supplemented by expert opinion and prior work. We chose measures that could be operationalized using national VA electronic health record (EHR) data. We assessed criterion validity for these 16 measures by manual review of 142 charts. Main outcome measures included positive and negative predictive values (PPVs, NPVs), overall accuracy (OA), and Matthews Correlation Coefficients (MCCs).

Results

We found high PPVs (>78%), NPVs (>98%), OA (≥94%), and MCCs (>0.85) for the 10 measures based on laboratory data (5 initiation and 5 monitoring). For the 6 measures relying on diagnostic codes, we similarly found high NPVs (100%) and OAs (≥98%). However, PPVs for measures of acute conditions occurring before testosterone initiation (ie, acute myocardial infarction or stroke) or new conditions occurring after initiation (ie, prostate or breast cancer) PPVs were much lower (0% to 50%) due to few or no cases.

Conclusion

We developed several valid EHR-based quality measures for assessing testosterone-prescribing practices. Deployment of these measures in health care systems can facilitate identification of quality gaps in testosterone-prescribing and improve care of men with hypogonadism.

Perceived benefits of geriatric specialty telemedicine among rural patients and caregivers

OBJECTIVE

Explore the perceived benefits of a Veterans Health Administration (VHA) geriatric specialty telemedicine service (GRECC Connect) among rural, older patients and caregivers to contribute to an assessment of its quality and value.

DATA SOURCES

In Spring 2021, we interviewed a geographically diverse sample of rural, older patients and their caregivers who participated in GRECC Connect telemedicine visits.

STUDY DESIGN

A cross-sectional qualitative study focused on patient and caregiver experiences with telemedicine, including perceived benefits and challenges.

DATA COLLECTION

We conducted 30 semi-structured qualitative interviews with rural, older (≥65) patients enrolled in the VHA and their caregivers via videoconference or phone. Interviews were recorded, transcribed, and analyzed using a rapid qualitative analysis approach.

PRINCIPAL FINDINGS

Participants described geriatric specialty telemedicine visits focused on cognitive assessments, tailored physical therapy, medication management, education on disease progression, support for managing multiple comorbidities, and suggestions to improve physical functioning. Participants reported that, in addition to prescribing medications and ordering tests, clinicians expedited referrals, coordinated care, and listened to and validated both patient and caregiver concerns. Perceived benefits included improved patient health; increased patient and caregiver understanding and confidence around symptom management; and greater feelings of empowerment, hopefulness, and support. Challenges included difficulty accessing some recommended programs and services, uncertainty related to instructions or follow-up, and not receiving as much information or treatment as desired. The content of visits was well aligned with the domains of the Age-Friendly Health Systems and Geriatric 5Ms frameworks (Medication, Mentation, Mobility, what Matters most, and Multi-complexity).

CONCLUSIONS

Alignment of patient and caregiver experiences with widely-used models of comprehensive geriatric care indicates that high-quality geriatric care can be provided through virtual modalities. Additional work is needed to develop strategies to address challenges and optimize and expand access to geriatric specialty telemedicine.

Innovative Approaches to Engaging Homeless and Marginally Housed Patients in Care: a Case Study of Hepatitis C

BACKGROUND

Homeless and marginally housed (HAMH) individuals experience significant health disparities compared to housed counterparts, including higher hepatitis C virus (HCV) rates. New direct-acting antiviral (DAA) medications dramatically increased screening and treatment rates for HCV overall, but inequities persist for HAMH populations.

OBJECTIVE

This study examines the range of policies, practices, adaptations, and innovations implemented by Veteran Affairs Medical Centers (VAMCs) in response to Veterans Health Administration (VHA)'s 2016 HCV funding allocation to expand provision of HCV care.

DESIGN

Ethnographic site visits to six US VAMCs varying in size, location, and availability of Homeless Patient-Aligned Care Teams. Semi-structured qualitative interviews informed by the HCV care continuum were conducted with providers, staff, and HAMH patients to elicit experiences providing and receiving HCV care. Semi-structured field note templates captured clinical care observations. Interview and observation data were analyzed to identify cross-cutting themes and strategies supporting tailored HCV care for HAMH patients.

PARTICIPANTS

Fifty-six providers and staff working in HCV and/or homelessness care (e.g., infectious disease providers, primary care providers, social workers). Twenty-five patients with varying homeless experiences, including currently, formerly, or at risk of homelessness (n=20) and stably housed (n=5).

KEY RESULTS

All sites experienced challenges with continued engagement of HAMH individuals in HCV care, which led to the implementation of targeted care strategies to better meet their needs. Across sites, we identified 35 unique strategies used to find, engage, and retain HAMH individuals in HCV care.

CONCLUSIONS

Despite highly effective, widely available HCV treatments, HAMH individuals continue to experience challenges accessing HCV care. VHA's 2016 HCV funding allocation resulted in rapid adoption of strategies to engage and retain vulnerable patients in HCV treatment. The strategies identified here can help healthcare institutions tailor and target approaches to provide sustainable, high-quality, equitable care to HAMH individuals living with HCV and other chronic illnesses.

PERSPECTIVES OF CAREGIVERS OF RURAL, OLDER VETERANS ON TELEGERIATRICS CARE

Telemedicine is critical to extending healthcare’s reach to rural older adults with complex medical needs, yet concerns remain about feasibility and acceptability for this population and their caregivers. We interviewed 30 rural Veterans ≥65 years old and/or their caregivers (n=21) about their experiences with video or telephone visits as part of an evaluation of Virtual Geriatrics, a network of Veterans Affairs tele-geriatric care hubs. Interviews were recorded, transcribed, and analyzed using rapid qualitative analysis. Caregivers deemed telemedicine a convenient option that prevented burdensome travel to remote specialists, facilitated caregiver involvement in visits, and matched quality of in-person visits. Caregivers often managed technology, enabling their loved one to participate in video visits. Telephone visits, while convenient, sometimes caused missed physical cues and hearing challenges which led providers to lean on caregiver communication. Our findings suggest telemedicine is feasible and acceptable for delivery for geriatrics care among rural adults and their caregivers.

Longitudinal high-frequency ethnographic interviewing to simulate and prepare for intensive smartphone data collection among veterans with homeless experience

Objective

While Veteran homelessness has steadily declined over the last decade, those who continue to be unhoused have complex health and social concerns. Housing instability interferes with access to healthcare, social services, and treatment adherence. Preventing unwanted housing transitions is a public health priority. This study is the first phase of a larger research agenda that aims to test the acceptability and feasibility of smartphone-enabled data collection with veterans experiencing homelessness. In preparation for the development of the smartphone data collection application, we utilized ethnographic methods guided by user-centered design principles to inform survey content, approach to recruitment and enrollment, and design decisions.

Methods

We used a case study design, selecting a small sample (n = 10) of veterans representing a range of homelessness experiences based on risk and length of time. Participants were interviewed up to 14 times over a 4-week period, using a combination of qualitative methods. Additionally, 2 focus group discussions were conducted. Interviews were audio-recorded and transcribed. Data were synthesized and triangulated through use of rapid analysis techniques.

Results

All participants had experience using smartphones and all but one owned one at the time of enrollment. Participants described their smartphones as “lifelines” to social network members, healthcare, and social service providers. Social relationships, physical and mental health, substance use, income, and housing environment were identified as being directly and indirectly related to transitions in housing. Over the course of ~30 days of engagement with participants, the research team observed dynamic fluctuations in emotional states, relationships, and utilization of services. These fluctuations could set off a chain of events that were observed to both help participants transition into more stable housing or lead to setbacks and further increase vulnerability and instability. In addition to informing the content of survey questions that will be programmed into the smartphone app, participants also provided a broad range of recommendations for how to approach recruitment and enrollment in the future study and design features that are important to consider for veterans with a range of physical abilities, concerns with trust and privacy, and vulnerability to loss or damage of smartphones.

Conclusion

The ethnographic approach guided by a user-centered design framework provided valuable data to inform our future smartphone data collection effort. Data were critical to understanding aspects of day-to-day life that important to content development, app design, and approach to data collection.

Dysmenorrhoea as a risk factor for pain with intrauterine device insertion

BACKGROUND

Understanding predictors of pain with gynaecological procedures may facilitate individualised counselling and pain management. We aimed to study the effect of dysmenorrhoea on intrauterine device (IUD) insertion pain.

METHODS

This was a planned secondary analysis of a randomised trial evaluating self-administered lidocaine gel versus placebo for IUD insertion pain. We included those participants who reported menses in the past 3 months. We assessed dysmenorrhoea (in the past 3 months) and procedural pain using a 100 mm visual analogue scale (VAS). We categorised dysmenorrhoea as none/mild (<40 mm), moderate (40-69 mm) or severe (≥70 mm). We assessed participant pain scores at speculum insertion, tenaculum placement, IUD insertion, and overall. We compared median procedural pain scores by dysmenorrhoea group with three-way and post hoc pairwise analyses.

RESULTS

We analysed 188 participants. Demographic characteristics were similar among the three dysmenorrhoea groups. Pairwise comparisons revealed higher median procedural pain scores in the severe dysmenorrhoea group compared with the none/mild dysmenorrhoea group at speculum insertion (25 mm vs 8 mm; p=0.007), tenaculum placement (51 mm vs 31 mm; p=0.04) and IUD insertion (74 mm vs 61 mm; p=0.04). Overall pain did not differ among the three groups (p=0.32).

CONCLUSIONS

Patients with severe dysmenorrhoea experienced increased pain with all aspects of IUD insertion, including speculum and tenaculum placement, compared with those with only mild or no dysmenorrhoea. Clinicians may consider this finding when providing individualised counselling and pain management for patients undergoing IUD insertion and other gynaecological procedures. Larger studies are needed to validate the effect of dysmenorrhoea severity on pain throughout IUD insertion.

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.

2361. Evaluation of a 2-Step Testing Algorithm for Clostridioides difficile Infection

Background

Clinical data describing use of a multistep algorithm for diagnosis of Clostridioides difficile infection (CDI) is limited. In June 2018 we implemented a 2-step testing algorithm in which PCR testing (Aries® assay) is performed for all specimens followed by EIA toxin testing (TOX A/B QUIK CHEK® assay) when PCR is positive. We sought to describe outcomes for patients with PCR+/EIA+ vs. PCR+/EIA− results. Outcomes evaluated included frequency of CDI treatment, retesting and retreatment within 3 months, and investigator determined categorization of C. difficile results by an investigator blinded to the EIA result.

Methods

A retrospective cohort study was performed on a random sample of 85 unique patients with a PCR+ stool sample from July 2018 through December 2018. Demographic and clinical data were abstracted from the medical record during the index encounter and for 3 months thereafter. Based on predetermined criteria, index encounter results were categorized as representing probable, possible, unlikely, or indeterminate cases of symptomatic CDI.

Results

For the 85 study patients, 42%, 27%, and 31% were tested in the inpatient, outpatient, and ED/urgent care settings. Twenty-seven patients (32%) were EIA+, all of whom received CDI treatment. Fifty-eight (68%) were EIA-, of which 79% received treatment. Of the 12 EIA- patient who did not receive treatment two had retesting within 3 months; one of whom subsequently tested EIA+ and was treated and the other tested PCR-. At least 1 C. difficile test was repeated within 3 months in 48% of EIA+ and 33% of EIA- patients. Based on repeat testing CDI treatment was prescribed for 12% of EIA+ subjects and for 11% of EIA- subjects. For the EIA+ patients, 70%, 19%, 7%, and 4% were classified as probable, possible, unlikely and indeterminate cases of symptomatic CDI when compared with 38%, 34%, 22%, and 5% for EIA- patients.

Conclusion

During the first 6 months of a 2-step testing algorithm, we found that patients with EIA- test results were frequently treated for CDI and that 72% of EIA- cases were classified as probably or possibly having symptomatic CDI. Further study is needed to determine whether patients with EIA- results categorized with probable or possible symptomatic CDI would improve without CDI treatment.

Disclosures

All authors: No reported disclosures.

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.

Comparison of keyboard colonization before and after use in an inpatient setting and the effect of keyboard covers

Computer keyboards may contribute to patient infections. We cultured new keyboards, with/without keyboard covers, before placing them in adult inpatient rooms and recultured after 6 months. Nonpathogenic bacteria were present initially but potentially pathogenic bacteria were cultured only after use. Coagulase negative Staphylococcus colonization increased after use (P < .001). Keyboards with a cover had more potentially pathogenic bacteria (22% vs 16%), which although not significant statistically (P = .72), likely due to sample size, trended against covers offering protection.

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.

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.

Monitoring 5-hydroxytryptamine release in the brain of the freely moving unanaesthetized rat using in vivo voltammetry

The possibility of using in vivo voltammetry to monitor 5-hydroxytryptamine (5-HT) release from brain tissue in freely moving unanaesthetized rats has been examined. A potential (+0.2 to +1.0 V) was applied to a micrographite electrode stereotaxically placed within a specific brain region and current changes following the oxidation of electroactive compounds in the vicinity of the electrode tip were recorded. Administration of p-chloroamphetamine (5 mg/kg) produced a large increase in current in the striatum and this could be prevented by pretreatment with p-chlorophenylalanine (150 mg/kg X 2) to deplete brain 5-HT or Fluoxetine (10 mg/kg) which prevents the uptake of p-chloroamphetamine by 5-HT neurones. Fluoxetine (10 mg/kg) caused a small but long lasting increase in current. Stimulation of the median raphe nucleus produced a marked and rapid rise in current in the hippocampus but a much smaller one in the striatum. This response could also be prevented by 24 h pretreatment with p-chlorophenylalanine (150 mg/kg). Seven days after p-chlorophenylalanine administration raphe stimulation again produced an increase in current. Rats under barbiturate anaesthesia showed no clear increase in current either after p-chloroamphetamine or raphe stimulation, indicating that barbiturates may affect neurotransmitter release. The results suggest that 5-HT release can be monitored in the freely moving unanaesthetized rat using in vivo voltammetry, and that a moderate decrease in brain 5-HT concentration leads to a substantial inhibition of drug or stimulation induced release of 5-HT.