Using Adaptive Bandit Experiments to Increase and Investigate Engagement in Mental Health

Digital mental health (DMH) interventions, such as text-message-based lessons and activities, offer immense potential for accessible mental health support. While these interventions can be effective, real-world experimental testing can further enhance their design and impact. Adaptive experimentation, utilizing algorithms like Thompson Sampling for (contextual) multi-armed bandit (MAB) problems, can lead to continuous improvement and personalization. However, it remains unclear when these algorithms can simultaneously increase user experience rewards and facilitate appropriate data collection for social-behavioral scientists to analyze with sufficient statistical confidence. Although a growing body of research addresses the practical and statistical aspects of MAB and other adaptive algorithms, further exploration is needed to assess their impact across diverse real-world contexts. This paper presents a software system developed over two years that allows text-messaging intervention components to be adapted using bandit and other algorithms while collecting data for side-by-side comparison with traditional uniform random non-adaptive experiments. We evaluate the system by deploying a text-message-based DMH intervention to 1100 users, recruited through a large mental health non-profit organization, and share the path forward for deploying this system at scale. This system not only enables applications in mental health but could also serve as a model testbed for adaptive experimentation algorithms in other domains.

Exploring User Perspectives on Brief Reflective Questioning Activities for Stress Management: Mixed Methods Study

BACKGROUND

Current online interventions dedicated to assisting individuals in managing stress and negative emotions often necessitate substantial time commitments. This can be burdensome for users, leading to high dropout rates and reducing the effectiveness of these interventions. This highlights an urgent need for concise digital activities that individuals can swiftly access during instances of negative emotions or stress in their daily lives.

OBJECTIVE

The primary aim of this study was to investigate the viability of using a brief digital exercise, specifically a reflective questioning activity (RQA), to help people reflect on their thoughts and emotions about a troubling situation. The RQA is designed to be quick, applicable to the general public, and scalable without requiring a significant support structure.

METHODS

We conducted 3 simultaneous studies. In the first study, we recruited 48 participants who completed the RQA and provided qualitative feedback on its design through surveys and semistructured interviews. In the second study, which involved 215 participants from Amazon Mechanical Turk, we used a between-participants design to compare the RQA with a single-question activity. Our hypotheses posited that the RQA would yield greater immediate stress relief and higher perceived utility, while not significantly altering the perception of time commitment. To assess these, we measured survey completion times and gathered multiple self-reported scores. In the third study, we assessed the RQA's real-world impact as a periodic intervention, exploring engagement via platforms such as email and SMS text messaging, complemented by follow-up interviews with participants.

RESULTS

In our first study, participants appreciated the RQA for facilitating structured reflection, enabling expression through writing, and promoting problem-solving. However, some of the participants experienced confusion and frustration, particularly when they were unable to find solutions or alternative perspectives on their thoughts. In the second study, the RQA condition resulted in significantly higher ratings (P=.003) for the utility of the activity and a statistically significant decrease (P<.001) in perceived stress rating compared with the single-question activity. Although the RQA required significantly more time to be completed (P<.001), there was no statistically significant difference in participants' subjective perceived time commitment (P=.37). Deploying the RQA over 2 weeks in the third study identified some potential challenges to consider for such activities, such as the monotony of doing the same activity several times, the limited affordances of mobile phones, and the importance of having the prompts align with the occurrence of new troubling situations.

CONCLUSIONS

This paper describes the design and evaluation of a brief online self-reflection activity based on cognitive behavioral therapy principles. Our findings can inform practitioners and researchers in the design and exploration of formats for brief interventions to help people with everyday struggles.

A flexible micro-randomized trial design and sample size considerations

Technological advancements have made it possible to deliver mobile health interventions to individuals. A novel framework that has emerged from such advancements is the just-in-time adaptive intervention, which aims to suggest the right support to the individuals when their needs arise. The micro-randomized trial design has been proposed recently to test the proximal effects of the components of these just-in-time adaptive interventions. However, the extant micro-randomized trial framework only considers components with a fixed number of categories added at the beginning of the study. We propose a more flexible micro-randomized trial design which allows addition of more categories to the components during the study. Note that the number and timing of the categories added during the study need to be fixed initially. The proposed design is motivated by collaboration on the Diabetes and Mental Health Adaptive Notification Tracking and Evaluation study, which learns to deliver effective text messages to encourage physical activity among patients with diabetes and depression. We developed a new test statistic and the corresponding sample size calculator for the flexible micro-randomized trial using an approach similar to the generalized estimating equation for longitudinal data. Simulation studies were conducted to evaluate the sample size calculators and an R shiny application for the calculators was developed.

Investigating the Role of Context in the Delivery of Text Messages for Supporting Psychological Wellbeing

Without a nuanced understanding of users' perspectives and contexts, text messaging tools for supporting psychological wellbeing risk delivering interventions that are mismatched to users' dynamic needs. We investigated the contextual factors that influence young adults' day-to-day experiences when interacting with such tools. Through interviews and focus group discussions with 36 participants, we identified that people's daily schedules and affective states were dominant factors that shape their messaging preferences. We developed two messaging dialogues centered around these factors, which we deployed to 42 participants to test and extend our initial understanding of users' needs. Across both studies, participants provided diverse opinions of how they could be best supported by messages, particularly around when to engage users in more passive versus active ways. They also proposed ways of adjusting message length and content during periods of low mood. Our findings provide design implications and opportunities for context-aware mental health management systems.

Ratings and experiences in using a mobile application to increase physical activity among university students: implications for future design

University students have low levels of physical activity and are at risk of mental health disorders. Mobile apps to encourage physical activity can help students, who are frequent smartphone-users, to improve their physical and mental health. Here we report students' qualitative feedback on a physical activity smartphone app with motivational text messaging. We provide recommendations for the design of future apps. 103 students used the app for 6 weeks in the context of a clinical trial (NCT04440553) and answered open-ended questions before the start of the study and at follow-up. A subsample (n = 39) provided additional feedback via text message, and a phone interview (n = 8). Questions focused on the perceived encouragement and support by the app, text messaging content, and recommendations for future applications. We analyzed all transcripts for emerging themes using qualitative coding in Dedoose. The majority of participants were female (69.9%), Asian or Pacific Islander (53.4%), with a mean age of 20.2 years, and 63% had elevated depressive symptoms. 26% felt encouraged or neutral toward the app motivating them to be more physically active. Participants liked messages on physical activity benefits on (mental) health, encouraging them to complete their goal, and feedback on their activity. Participants disliked messages that did not match their motivations for physical activity and their daily context (e.g., time, weekday, stress). Physical activity apps for students should be adapted to their motivations, changing daily context, and mental health issues. Feedback from this sample suggests a key to effectiveness is finding effective ways to personalize digital interventions.

"I Kind of Bounce off It": Translating Mental Health Principles into Real Life Through Story-Based Text Messages

Adopting new psychological strategies to improve mental wellness can be challenging since people are often unable to anticipate how new habits are applicable to their circumstances. Narrative-based interventions have the potential to alleviate this burden by illustrating psychological principles in an applied context. In this work, we explore how stories can be delivered via the ubiquitous and scalable medium of text messaging. Through formative work consisting of interviews and focus group discussions with 15 participants, we identified desirable elements of stories about mental health, including authenticity and relatability. We then deployed story-based text messages to 42 participants to explore challenges regarding both the stories' content (e.g., specific versus generalized) and format (e.g., story length). We observed that our stories helped participants reflect on and identify flaws in their thinking patterns. Our findings highlight design implications and opportunities for mental wellness interventions that utilize stories in text messaging services.

Adaptive learning algorithms to optimize mobile applications for behavioral health: guidelines for design decisions

OBJECTIVE

Providing behavioral health interventions via smartphones allows these interventions to be adapted to the changing behavior, preferences, and needs of individuals. This can be achieved through reinforcement learning (RL), a sub-area of machine learning. However, many challenges could affect the effectiveness of these algorithms in the real world. We provide guidelines for decision-making.

MATERIALS AND METHODS

Using thematic analysis, we describe challenges, considerations, and solutions for algorithm design decisions in a collaboration between health services researchers, clinicians, and data scientists. We use the design process of an RL algorithm for a mobile health study "DIAMANTE" for increasing physical activity in underserved patients with diabetes and depression. Over the 1.5-year project, we kept track of the research process using collaborative cloud Google Documents, Whatsapp messenger, and video teleconferencing. We discussed, categorized, and coded critical challenges. We grouped challenges to create thematic topic process domains.

RESULTS

Nine challenges emerged, which we divided into 3 major themes: 1. Choosing the model for decision-making, including appropriate contextual and reward variables; 2. Data handling/collection, such as how to deal with missing or incorrect data in real-time; 3. Weighing the algorithm performance vs effectiveness/implementation in real-world settings.

CONCLUSION

The creation of effective behavioral health interventions does not depend only on final algorithm performance. Many decisions in the real world are necessary to formulate the design of problem parameters to which an algorithm is applied. Researchers must document and evaulate these considerations and decisions before and during the intervention period, to increase transparency, accountability, and reproducibility.

TRIAL REGISTRATION

clinicaltrials.gov, NCT03490253.

Developing Messaging Content for a Physical Activity Smartphone App Tailored to Low-Income Patients: User-Centered Design and Crowdsourcing Approach

Background

Text messaging interventions can be an effective and efficient way to improve health behavioral changes. However, most texting interventions are neither tested nor designed with diverse end users, which could reduce their impact, and there is limited evidence regarding the optimal design methodology of health text messages tailored to low-income, low–health literacy populations and non-English speakers.

Objective

This study aims to combine participant feedback, crowdsourced data, and researcher expertise to develop motivational text messages in English and Spanish that will be used in a smartphone app–based texting intervention that seeks to encourage physical activity in low-income minority patients with diabetes diagnoses and depression symptoms.

Methods

The design process consisted of 5 phases and was iterative in nature, given that the findings from each step informed the subsequent steps. First, we designed messages to increase physical activity based on the behavior change theory and knowledge from the available evidence. Second, using user-centered design methods, we refined these messages after a card sorting task and semistructured interviews (N=10) and evaluated their likeability during a usability testing phase of the app prototype (N=8). Third, the messages were tested by English- and Spanish-speaking participants on the Amazon Mechanical Turk (MTurk) crowdsourcing platform (N=134). Participants on MTurk were asked to categorize the messages into overarching theoretical categories based on the capability, opportunity, motivation, and behavior framework. Finally, each coauthor rated the messages for their overall quality from 1 to 5. All messages were written at a sixth-grade or lower reading level and culturally adapted and translated into neutral Spanish by bilingual research staff.

Results

A total of 200 messages were iteratively refined according to the feedback from target users gathered through user-centered design methods, crowdsourced results of a categorization test, and an expert review. User feedback was leveraged to discard unappealing messages and edit the thematic aspects of messages that did not resonate well with the target users. Overall, 54 messages were sorted into the correct theoretical categories at least 50% of the time in the MTurk categorization tasks and were rated 3.5 or higher by the research team members. These were included in the final text message bank, resulting in 18 messages per motivational category.

Conclusions

By using an iterative process of expert opinion, feedback from participants that were reflective of our target study population, crowdsourcing, and feedback from the research team, we were able to acquire valuable inputs for the design of motivational text messages developed in English and Spanish with a low literacy level to increase physical activity. We describe the design considerations and lessons learned for the text messaging development process and provide a novel, integrative framework for future developers of health text messaging interventions.

Daily Motivational Text Messages to Promote Physical Activity in University Students: Results From a Microrandomized Trial

BACKGROUND

Low physical activity is an important risk factor for common physical and mental disorders. Physical activity interventions delivered via smartphones can help users maintain and increase physical activity, but outcomes have been mixed.

PURPOSE

Here we assessed the effects of sending daily motivational and feedback text messages in a microrandomized clinical trial on changes in physical activity from one day to the next in a student population.

METHODS

We included 93 participants who used a physical activity app, "DIAMANTE" for a period of 6 weeks. Every day, their phone pedometer passively tracked participants' steps. They were microrandomized to receive different types of motivational messages, based on a cognitive-behavioral framework, and feedback on their steps. We used generalized estimation equation models to test the effectiveness of feedback and motivational messages on changes in steps from one day to the next.

RESULTS

Sending any versus no text message initially resulted in an increase in daily steps (729 steps, p = .012), but this effect decreased over time. A multivariate analysis evaluating each text message category separately showed that the initial positive effect was driven by the motivational messages though the effect was small and trend-wise significant (717 steps; p = .083), but not the feedback messages (-276 steps, p = .4).

CONCLUSION

Sending motivational physical activity text messages based on a cognitive-behavioral framework may have a positive effect on increasing steps, but this decreases with time. Further work is needed to examine using personalization and contextualization to improve the efficacy of text-messaging interventions on physical activity outcomes.

CLINICALTRIALS.GOV IDENTIFIER

NCT04440553.

Nonprofessional Peer Support to Improve Mental Health: Randomized Trial of a Scalable Web-Based Peer Counseling Course

BACKGROUND

Millions of people worldwide are underserved by the mental health care system. Indeed, most mental health problems go untreated, often because of resource constraints (eg, limited provider availability and cost) or lack of interest or faith in professional help. Furthermore, subclinical symptoms and chronic stress in the absence of a mental illness diagnosis often go unaddressed, despite their substantial health impact. Innovative and scalable treatment delivery methods are needed to supplement traditional therapies to fill these gaps in the mental health care system.

OBJECTIVE

This study aims to investigate whether a self-guided web-based course can teach pairs of nonprofessional peers to deliver psychological support to each other.

METHODS

In this experimental study, a community sample of 30 dyads (60 participants, mostly friends), many of whom presented with mild to moderate psychological distress, were recruited to complete a web-based counseling skills course. Dyads were randomized to either immediate or delayed access to training. Before and after training, dyads were recorded taking turns discussing stressors. Participants' skills in the helper role were assessed before and after taking the course: the first author and a team of trained research assistants coded recordings for the presence of specific counseling behaviors. When in the client role, participants rated the session on helpfulness in resolving their stressors and supportiveness of their peers. We hypothesized that participants would increase the use of skills taught by the course and decrease the use of skills discouraged by the course, would increase their overall adherence to the guidelines taught in the course, and would perceive posttraining counseling sessions as more helpful and their peers as more supportive.

RESULTS

The course had large effects on most helper-role speech behaviors: helpers decreased total speaking time, used more restatements, made fewer efforts to influence the speaker, and decreased self-focused and off-topic utterances (ds=0.8-1.6). When rating the portion of the session in which they served as clients, participants indicated that they made more progress in addressing their stressors during posttraining counseling sessions compared with pretraining sessions (d=1.1), but they did not report substantive changes in feelings of closeness and supportiveness of their peers (d=0.3).

CONCLUSIONS

The results provide proof of concept that nonprofessionals can learn basic counseling skills from a scalable web-based course. The course serves as a promising model for the development of web-based counseling skills training, which could provide accessible mental health support to some of those underserved by traditional psychotherapy.

mHealth app using machine learning to increase physical activity in diabetes and depression: clinical trial protocol for the DIAMANTE Study

INTRODUCTION

Depression and diabetes are highly disabling diseases with a high prevalence and high rate of comorbidity, particularly in low-income ethnic minority patients. Though comorbidity increases the risk of adverse outcomes and mortality, most clinical interventions target these diseases separately. Increasing physical activity might be effective to simultaneously lower depressive symptoms and improve glycaemic control. Self-management apps are a cost-effective, scalable and easy access treatment to increase physical activity. However, cutting-edge technological applications often do not reach vulnerable populations and are not tailored to an individual's behaviour and characteristics. Tailoring of interventions using machine learning methods likely increases the effectiveness of the intervention.

METHODS AND ANALYSIS

In a three-arm randomised controlled trial, we will examine the effect of a text-messaging smartphone application to encourage physical activity in low-income ethnic minority patients with comorbid diabetes and depression. The adaptive intervention group receives messages chosen from different messaging banks by a reinforcement learning algorithm. The uniform random intervention group receives the same messages, but chosen from the messaging banks with equal probabilities. The control group receives a weekly mood message. We aim to recruit 276 adults from primary care clinics aged 18-75 years who have been diagnosed with current diabetes and show elevated depressive symptoms (Patient Health Questionnaire depression scale-8 (PHQ-8) >5). We will compare passively collected daily step counts, self-report PHQ-8 and most recent haemoglobin A1c from medical records at baseline and at intervention completion at 6-month follow-up.

ETHICS AND DISSEMINATION

The Institutional Review Board at the University of California San Francisco approved this study (IRB: 17-22608). We plan to submit manuscripts describing our user-designed methods and testing of the adaptive learning algorithm and will submit the results of the trial for publication in peer-reviewed journals and presentations at (inter)-national scientific meetings.

TRIAL REGISTRATION NUMBER

NCT03490253; pre-results.

Scaling up behavioral science interventions in online education

Online education is rapidly expanding in response to rising demand for higher and continuing education, but many online students struggle to achieve their educational goals. Several behavioral science interventions have shown promise in raising student persistence and completion rates in a handful of courses, but evidence of their effectiveness across diverse educational contexts is limited. In this study, we test a set of established interventions over 2.5 y, with one-quarter million students, from nearly every country, across 247 online courses offered by Harvard, the Massachusetts Institute of Technology, and Stanford. We hypothesized that the interventions would produce medium-to-large effects as in prior studies, but this is not supported by our results. Instead, using an iterative scientific process of cyclically preregistering new hypotheses in between waves of data collection, we identified individual, contextual, and temporal conditions under which the interventions benefit students. Self-regulation interventions raised student engagement in the first few weeks but not final completion rates. Value-relevance interventions raised completion rates in developing countries to close the global achievement gap, but only in courses with a global gap. We found minimal evidence that state-of-the-art machine learning methods can forecast the occurrence of a global gap or learn effective individualized intervention policies. Scaling behavioral science interventions across various online learning contexts can reduce their average effectiveness by an order-of-magnitude. However, iterative scientific investigations can uncover what works where for whom.

Developing nursing research in the United Arab Emirates: a narrative review

AIM

This article identified, critically analysed and synthesized the literature on international nursing and midwifery research capacity building and standards.

BACKGROUND

The United Arab Emirates is heavily dependent up on expatriate nurses. Only 4% of nurses working within the country are Emirati. The nation is therefore committed to developing nurses and nursing as a profession.

INTRODUCTION

The United Arab Emirates' Nursing and Midwifery Council was formed in 2009 and initially focused on regulation, education and specialization. This review was undertaken to inform the work of the Council's newly established Scientific Research Sub-Committee.

METHODS

A rapid narrative review was conducted using the Cumulative Index of Nursing and Allied Health Literature database, key words, Boolean operators, parameters and a journal-specific search. An inclusion/exclusion criterion was identified.

RESULTS

The search provided 332 articles with 45 included in the final review. The literature on nursing research 'standards' and 'capacity building' is diverse and inconsistent across continents and in approaches.

DISCUSSION

Nursing research has evolved to varying degrees across the globe. Nevertheless, irrespective of the locale, there are similar problems encountered in growing research, for example nursing faculty shortage, lack of collaborative research, funding. There are also specific challenges in the Middle East and North Africa region.

LIMITATIONS

The review was constrained by time and access.

CONCLUSION AND IMPLICATIONS FOR NURSING POLICY

There are specific challenges for the United Arab Emirates. However, the country is well placed to learn from the experiences of colleagues elsewhere. Time and commitment is required to build the solid foundations necessary to ensure robust, sustained growth. Identifying research capacity as both a process and outcome at the outset may also assist. Further, it may be prudent to consider initiating a Gulf Coast Countries' collaborative approach to building research capacity to harness scare resources and create a larger critical mass.

Spatial co-adaptation of cortical control columns in a micro-ECoG brain-computer interface

OBJECTIVE

Electrocorticography (ECoG) has been used for a range of applications including electrophysiological mapping, epilepsy monitoring, and more recently as a recording modality for brain-computer interfaces (BCIs). Studies that examine ECoG electrodes designed and implanted chronically solely for BCI applications remain limited. The present study explored how two key factors influence chronic, closed-loop ECoG BCI: (i) the effect of inter-electrode distance on BCI performance and (ii) the differences in neural adaptation and performance when fixed versus adaptive BCI decoding weights are used.

APPROACH

The amplitudes of epidural micro-ECoG signals between 75 and 105 Hz with 300 μm diameter electrodes were used for one-dimensional and two-dimensional BCI tasks. The effect of inter-electrode distance on BCI control was tested between 3 and 15 mm. Additionally, the performance and cortical modulation differences between constant, fixed decoding using a small subset of channels versus adaptive decoding weights using the entire array were explored.

MAIN RESULTS

Successful BCI control was possible with two electrodes separated by 9 and 15 mm. Performance decreased and the signals became more correlated when the electrodes were only 3 mm apart. BCI performance in a 2D BCI task improved significantly when using adaptive decoding weights (80%-90%) compared to using constant, fixed weights (50%-60%). Additionally, modulation increased for channels previously unavailable for BCI control under the fixed decoding scheme upon switching to the adaptive, all-channel scheme.

SIGNIFICANCE

Our results clearly show that neural activity under a BCI recording electrode (which we define as a 'cortical control column') readily adapts to generate an appropriate control signal. These results show that the practical minimal spatial resolution of these control columns with micro-ECoG BCI is likely on the order of 3 mm. Additionally, they show that the combination and interaction between neural adaptation and machine learning are critical to optimizing ECoG BCI performance.

Note: design and construction of a multi-scale, high-resolution, tube-generated x-ray computed-tomography system for three-dimensional (3D) imaging

The design and construction of a high resolution modular x-ray computed tomography (XCT) system is described. The approach for meeting a specified set of performance goals tailored toward experimental versatility is highlighted. The instrument is unique in its detector and x-ray source configuration, both of which enable elevated optimization of spatial and temporal resolution. The process for component selection is provided. The selected components are specified, the custom component design discussed, and the integration of both into a fully functional XCT instrument is outlined. The novelty of this design is a new lab-scale detector and imaging optimization through x-ray source and detector modularity.

An HMM-based speech-to-video synthesizer

Emerging broadband communication systems promise a future of multimedia telephony, e.g. the addition of visual information to telephone conversations. It is useful to consider the problem of generating the critical information useful for speechreading, based on existing narrowband communications systems used for speech. This paper focuses on the problem of synthesizing visual articulatory movements given the acoustic speech signal. In this application, the acoustic speech signal is analyzed and the corresponding articulatory movements are synthesized for speechreading. This paper describes a hidden Markov model (HMM)-based visual speech synthesizer. The key elements in the application of HMMs to this problem are the decomposition of the overall modeling task into key stages and the judicious determination of the observation vector's components for each stage. The main contribution of this paper is a novel correlation HMM model that is able to integrate independently trained acoustic and visual HMMs for speech-to-visual synthesis. This model allows increased flexibility in choosing model topologies for the acoustic and visual HMMs. Moreover the propose model reduces the amount of training data compared to early integration modeling techniques. Results from objective experiments analysis show that the propose approach can reduce time alignment errors by 37.4% compared to conventional temporal scaling method. Furthermore, subjective results indicated that the purpose model can increase speech understanding.

Performance of the new generation of whole-body PET/CT scanners: Discovery STE and Discovery VCT

PURPOSE

The new GE Discovery STE and Discovery VCT respectively combine 16-slice and 64-slice CT with PET. The PET scanner has a new BGO detector block of 8 x 6 matrix (6.3 x 4.7 x 30 mm(3)). The aim of this study was to test the performance of the new scanner.

METHODS

The PET performance evaluation was done using NEMA methodology. Owing to improved front-end electronics, the system was tested with different energy window and coincidence timing settings.

RESULTS

Transaxial resolution FWHM for 2D(3D) mode at 1 cm offset from the centre of the field of view (R1) was 4.87 mm (5.12 mm) and at 10 cm off centre (R10) radially 5.70 mm (5.89 mm) and tangentially 5.84 mm (5.47 mm). The axial resolutions were 4.4 mm (5.18 mm) (R1) and 5.99 mm (5.86 mm) (R10). The sensitivities were 2.3 cps/kBq (8.8 cps/kBq) (R0, centre of field of view) and 2.3 cps/kBq (8.9 cps/kBq) (R10). The system scatter fraction was 21.4% in 2D at an energy of 375 keV (33.9% in 3D mode at a higher energy of 425 keV). Peak noise equivalent count rates (k=1) were 84.9 kcps at 43.9 kBq/ml (2D) and 67.6 kcps at 12.1 kBq/ml (3D). In image quality measurement the hot sphere to background contrast with 10- to 22-mm diameter spheres varied from 14% to 68%, being slightly better in 3D than in 2D mode. Cold sphere contrast was 67% in 2D and 59% in 3D mode.

CONCLUSION

GE's new STE and VCT PET/CT systems have improved spatial resolution without loss in sensitivity. When compared with the LYSO crystal-based GE Discovery RX, the resolution and scatter fraction are comparable, the count rate capability is lower but the sensitivity is higher.

Spatial distribution of acaricide profiles (Boophilus microplus strains susceptible or resistant to acaricides) in southeastern Mexico

The ability of Boophilus microplus strains to be susceptible (-) or resistant (+) to amidines (Am), synthetic pyrethroids (SP), and/or organo-phosphates (OP) (or acaricide profiles) was investigated in 217 southeastern Mexican cattle ranches (located in the states of Yucatán, Quintana Roo, and Tabasco). Three questions were asked: (1) whether acaricide profiles varied at random and, if not, which one(s) explained more (or less) cases than expected, (2) whether the spatial distribution of acaricide profiles was randomly or non-randomly distributed, and (3) whether acaricide profiles were associated with farm-related covariates (frequency of annual treatments, herd size, and farm size). Three acaricide profiles explained 73.6% of the data, representing at least twice as many cases as expected (P<0.001): (1) Am-SP-, (2) Am+SP+, and (3) (among ranches that dispensed acaricides > or = 6 times/year) Am-OP+SP+. Because ticks collected in Yucatán ranches tended to be susceptible to Am, those of Quintana Roo ranches displayed, predominantly, resistance to OP/SP, and Tabasco ticks tended to be resistant to Am (all with P < or = 0.05), acaricide profiles appeared to be non-randomly disseminated over space. Across states, two farm-related covariates were associated with resistance (P < or = 0.02): (1) high annual frequency of acaricide treatments, and (2) large farm size. Findings supported the hypothesis that spatial acaricide profiles followed neither random nor homogeneous data distributions, being partially explained by agent- and/or farm-specific factors. Some profiles could not be explained by these factors. Further spatially explicit studies (addressing host-related factors) are recommended.

The calcium-sensing receptor regulates calcium absorption in MDCK cells by inhibition of PMCA

Calcium transport across a monolayer of Madin-Darby canine kidney (MDCK) cells was measured in response to stimulation of the basal surface with calcium-sensing receptor (CaR) agonists. Stimulation of the CaR resulted in a time- and concentration-dependent inhibition of calcium transport but did not change transepithelial voltage or resistance. Inhibition of transport was not altered by pretreatment of cells with pertussis toxin but was blocked by the phospholipase C (PLC) inhibitor U-73122. To determine a potential mechanism by which the CaR could inhibit calcium transport, we measured activity of the plasma membrane calcium ATPase (PMCA). Stimulation of the CaR on the basal surface resulted in an inhibition of the PMCA in a concentration- and PLC-dependent manner. Thus stimulation of the CaR inhibits both calcium transport and PMCA activity through a PLC-dependent pathway. These studies provide the first direct evidence that calcium can inhibit its own transcellular absorption in a model of the distal tubule. In addition, they provide a potential mechanism for the CaR to inhibit calcium transport, inhibition of PMCA.

Investigation of risk factors for porcine Taenia solium cysticercosis: a multiple regression analysis of a cross-sectional study in the Yucatan Peninsula, Mexico

A cross-sectional survey for seropositivity to cysticercosis of pigs in the Yucatan Peninsula, Mexico, was carried out in 1996 together with a standardized questionnaire on predetermined individual pig and household risk factors for porcine infection. Serum samples from 697 pigs were analysed by immunoblot for antibodies to Taenia solium cysticercosis and questionnaires from 227 households in 18 villages were collected. All the data were analysed using multivariate analytical techniques taking household clustering into account. The overall porcine seroprevalence in the area was found to be 29%. The most important risk factors for seropositivity in pigs were presence versus absence of a toilet (adjusted odds ratio [adj. OR] 2.37, P = 0.005), crowded households (adj. OR 1.75, P = 0.034) and both corralling (adj. OR 2.14, P = 0.017) and letting pigs loose (adj. OR 2.32, P = 0.035) versus tying them up. There was evidence of clustering at household level and that possible risk factors at municipal or village level may also interact with higher risk management practices such as allowing pigs to run loose.

Performance characteristics of a whole-body PET scanner

METHODS

This study characterizes the performance of a newly developed whole-body PET scanner (Advance, General Electric Medical Systems, Milwaukee, WI). The scanner consists of 12,096 bismuth germinate crystals (4.0 mm transaxial by 8.1 mm axial by 30 mm radial) in 18 rings, giving 35 two-dimensional image planes through an axial field of view of 15.2 cm. The rings are separated by retractable tungsten septa. Intrinsic spatial resolution, scatter fraction, sensitivity, high count rate performance and image quality are evaluated.

RESULTS

Transaxial resolution (in FWHM) is 3.8 mm at the center and increases to 5.0 mm tangential and 7.3 mm radial at R = 20 cm. Average axial resolution decreases from 4.0 mm FWHM at the center to 6.6 mm at R = 20 cm. Scatter fraction is 9.4% and 10.2% for direct and cross slices, respectively. With septa out, the average scatter fraction is 34%. Total system sensitivity for true events (in kcps/(microCi/cc)) is 223 with septa in and 1200 with septa out. Dead-time losses of 50% correspond to a radioactivity concentration of 4.9 (0.81) microCi/cc and a true event count rate of 489 (480) kcps with septa in (out). Noise-equivalent count rate (NECR) for the system as a whole shows a maximum of 261 (159) kcps at a radioactivity concentration of 4.1 (0.65) microCi/cc with septa in (out). NECR is insensitive to changes in lower gamma-energy discrimination between 250-350 keV.

CONCLUSIONS

The results show the performance of the newly designed PET scanner to be well suited for clinical and research applications.

Late knee problems in myelomeningocele

This study was undertaken to assess the incidence and etiology of knee problems in a long-term follow-up of myelomeningocele patients. Of the 72 community ambulators reviewed, 17 (24%) had significant knee symptoms. A specific gait pattern was identified in symptomatic patients with low lumbar lesions, which may be explained on the basis of hip abductor and calf muscle weakness. These patients have a characteristic gait, which places abnormal stress on the knee, leading to medial and anteromedial rotary instability and eventual degenerative change. It is likely that disability resulting from knee symptoms will be the factor precluding independent ambulation in the patients reviewed in this study.

Evolution of femoral head deformity during the healing phase of Legg-Calvé-Perthes disease

Progressive changes in the roundness of the femoral head were noted during the healing phase of hips with Legg-Calvé-Perthes disease. Forty-nine of 136 hips studied became progressively rounder, and 15 hips became progressively flatter after onset of reossification of the femoral head. The femoral head was more likely to undergo progressive flattening in older patients, in those with more severe lateral pillar involvement, and in those with prolonged reossification. These changes occurred during a 3- to 4-year reossification period after cessation of treatment.

The lateral pillar classification of Legg-Calvé-Perthes disease

To determine the predictive value of a new classification system for Legg-Perthes, 93 hips in 86 patients with radiographic follow-up to maturity were reviewed. All patients were treated by bracing at the Texas Scottish Rite Hospital from 1970 to 1980. Hips were classified during the fragmentation stage of disease into three groups based on radiolucency in the lateral pillar of the femoral head. Final radiographs were reviewed at skeletal maturity, and the outcome was determined according to the Stulberg classification. Group A had a uniformly good outcome (100% Stulberg I and II results); Group B had a good outcome in patients who were less than 9 years at onset (92% Stulberg I and II, 8% Stulberg III results), but a less favorable outcome in patients who were greater than 9 years at onset (30% Stulberg II, 50% Stulberg III, and 20% Stulberg IV results). In Group C, the majority of femoral heads became aspherical in both age groups (29% Stulberg II, 52% Stulberg III, and 19% Stulberg IV results). The group C hips also had a longer duration of fragmentation and reossification stages. Members of the Legg-Perthes study group agreed 78% of the time when applying the classification to unknown radiographs. The classification group was a stronger determinant than age of onset in predicting final outcome. This classification system is easy to apply during the active stage of the disease and has a high correlation in predicting the amount of flattening of the femoral head at skeletal maturity.(ABSTRACT TRUNCATED AT 250 WORDS)

Radial neck fracture complicating closed reduction of a posterior elbow dislocation in a child: case report

A case of radial neck fracture complicating repeated attempts at closed reduction of a posterior elbow dislocation in a child is described. This case underscores the necessity of using proper technique when reducing posterior elbow dislocations. The mechanism of radial neck fracture in association with posterior elbow dislocation is discussed.

Pulmonary endothelial injury and altered fibrinolysis after femur fracture in rabbits

The pathophysiology of acute lung injury after long bone fracture may be associated with endothelial damage and altered fibrinolysis. Accordingly, we studied metabolic functions of pulmonary endothelial cells: 5-hydroxytryptamine (5-HT) uptake and angiotensin-converting enzyme (ACE) activity in anesthetized rabbits before and every 4 h after long bone fracture (n = 12) or sham (n = 6). To assess changes in fibrinolysis, we studied levels of plasminogen activator inhibitor (PAI), an inhibitor of the fibrinolytic cascade. All animals in the control group and only 6 of 12 animals in the long bone fracture group survived 12 h. 5-HT uptake was depressed after 8 h in both groups. By 12 h, however, 5-HT uptake in the long bone fracture group remained depressed, but returned to baseline in the control group. Conversely, ACE activity was unchanged in both groups. PAI levels were increased in both groups at 4 h. During the next 8 h, levels in the long bone fracture group continued to increase and remained elevated, whereas levels in the control group decreased and were not greater than baseline at 12 h. Initial PAI and 5-HT uptake changes may be related to surgical preparation of the rabbit. Prolonged depression of 5-HT uptake suggests that musculoskeletal trauma is associated with pulmonary endothelial damage. Finally, impaired fibrinolysis due to increased PAI may contribute to the pathogenesis of endothelial injury after long bone fracture.

Radial growth and function of the forearm after excision of the radial head. A study of growing macaque monkeys

In five immature macaque monkeys, the right radial head was excised and the left forearm served as a control. Growth of each radius, ulna, and proximal and distal physis was followed for eight years. Total radial growth was slightly less on the side that was operated on than it was on the control side. After excision of the radial head, 95 per cent of radial growth came from the distal physis, compared with 71 per cent on the control side. A regenerated radial head, which had an irregular surface of fibrocartilaginous tissue, accounted for the remainder of growth on the side that had been operated on. Incongruous contact of articular surfaces resulted in degenerative changes in the capitellum. The arms that had been operated on were left with a flexion contracture that was an average of 12 degrees greater than that of the normal elbows, and they had a carrying angle that was an average of 6 degrees greater than that on the normal side. The arc of pronation and supination was decreased for the forearms that had been operated on, but motion of the wrist was unaffected. In our study, excision of the radial head in growing monkeys resulted in minimum radial shortening, slight deformity of the elbow, and moderate impairment of rotation of the forearm.

Respiratory infections caused by Branhamella catarrhalis. Selected epidemiologic features

PURPOSE

This work reviewed existing literature pertaining to the epidemiologic aspects of respiratory tract infections caused by Branhamella catarrhalis, examined certain epidemiologic features of B. catarrhalis infections occurring at this facility, and identified relevant areas in need of further study.

PATIENTS AND METHODS

Literature dealing with the epidemiology of B. catarrhalis infections was reviewed. Records in this Veterans Administration hospital microbiology laboratory were reviewed and all B. catarrhalis isolates and pure cultures of Hemophilus influenzae and Streptococcus pneumoniae were noted for the January 1986 to June 1989 study period.

RESULTS

B. catarrhalis is now recognized as a disease-causing pathogen that is particularly noted for its association with acute otitis media in children and lower respiratory tract infections in adults with underlying cardiopulmonary disease. It was recovered from 2.7 percent of all respiratory specimens submitted over a 42-month period at this Veterans hospital. When compared with H. influenzae and S. pneumoniae, B. catarrhalis was found to be the second most commonly isolated respiratory pathogen. It was frequently found in pure culture (53 percent) or in combination with H. influenzae, gram-negative bacilli, or S. pneumoniae. The seasonal recovery of B. catarrhalis was apparent for the November to May period compared with the June to October period (p less than 0.001).

CONCLUSION

B. catarrhalis has emerged as a major respiratory pathogen in pediatric and adult patient populations. There is a distinct seasonal pattern associated with its recovery and reasons for this are unclear. Prevalence studies aimed at identifying colonization rates among "low" and "high" risk groups are needed. The availability of restriction endonuclease analysis as a typing system for B. catarrhalis should favorably impact upon future epidemiologic studies. Many B. catarrhalis isolates produce beta-lactamase, and therapeutic options must reflect this.

The effect of ultraviolet B radiation treatments on calcium excretion and vitamin D metabolites in kidney stone formers

Several factors could explain the effect of warm, sunny weather on kidney stone formation. To determine the role of sun exposure, we used a light box to administer artificial ultraviolet B radiation during the winter months in New York City. Eleven male stone formers and 7 age- and sex-matched controls received 10 UVB light exposures over a two-week period while maintaining a 400 mg calcium diet. 25-OH vitamin D levels increased significantly (p less than 0.001) in both patients (25.9 +/- 9.8 to 51.6 +/- 14.1 ng/ml) and controls (21.3 +/- 7.1 to 49.6 +/- 3.1 ng/ml). However, 1,25 dihydroxyvitamin D levels rose in the patients (50.8 +/- 14.8 to 55.9 +/- 13.1 pg/ml) but fell (60.1 +/- 6.5 to 49.4 +/- 3.1 pg/ml) in the controls. Only 2 of the 11 patients but all of the controls demonstrated this down regulation of 1,25 dihydroxyvitamin D levels (p less than 0.002). 24,25 dihydroxyvitamin D levels tended to rise in both groups but parathyroid hormone levels were unchanged. There was a trend, which did not reach statistical significance, for parameters of calcium excretion to increase after UVB radiation. 24-hour urinary calcium excretion rose 24% from 140 to 173 mg in the patients and 31% from 113 to 148 mg in the controls. The ratio of calcium/creatinine following a one gram calcium load showed a small increase after UVB radiation from 0.17 to 0.20 in patients and 0.118 to 0.124 in the controls. However, no correlation could be discerned between changes in vitamin D metabolite concentrations and changes in urinary calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilateral ureteral obstruction secondary to condylomata acuminata of the urinary bladder

Condyloma acuminatum is a viral infection of near epidemic proportions. Both men and women are affected equally. Most lesions are on the external genitalia and the mucous membranes of the urethra or the vagina. A rare occurrence of condyloma acuminata is involvement of the urinary bladder. To date, only 11 cases have been reported. We describe two additional cases, both with bilateral ureteral obstruction. Current urologic management and review of the literature are presented.

The effect of pleural pressure on the hypoxic pulmonary vasoconstrictor response in closed chest dogs

The effect of intrapleural pressure on the hypoxic pulmonary vasoconstrictor (HPV) responses to atelectasis and hypoxia were measured in two groups of anesthetized closed chest dogs. The right lung was continuously ventilated with 100% O2. The left lung was initially ventilated with 100% O2 (hyperoxia) but subsequently underwent either reabsorption atelectasis (atelectasis; group I) or ventilation with a hypoxic gas mixture (hypoxia; group II). The mean intrapleural pressure in the left hemithorax was 5.4 cm H2O during hyperoxia, but with left lung atelectasis decreased significantly to -3.8 cm H2O by 15 minutes and to -4.2 cm H2O by 90 minutes. Venous admixture (% VA) increased significantly from 10.3% during hyperoxia to 33.2% at 15 minutes of left lung atelectasis and to 34.6% at 90 minutes. However, after sternotomy with the left lung still atelectatic, the %VA decreased significantly to 25.4% For the hypoxia group, %VA increased significantly from 9.2% during hyperoxia to 29.9% at 15 minutes of left lung hypoxia and 25.1% at 90 minutes. HPV diverted blood flow away from both atelectatic lung and hypoxic lung. However, due to the negative intrapleural pressure generated during left lung resorption atelectasis when the chest was closed, HPV was less effective during atelectasis than during hypoxia.

New methods of examining gamma camera collimators

New methods are proposed and described to examine the quality of gamma camera collimators in two special performance categories, namely, uniformity in regional efficiency and regional variations in channel tilt. These two performances are critical areas for SPECT imaging. Results obtained from experimental and commercial collimators illustrate the variability seen for these performance characteristics in currently available collimators.

Hypercoagulability produced by treatment with acetohydroxamic acid

Thrombosis has been observed with unusual frequency in patients receiving acetohydroxamic acid (AHA) for treatment of struvite nephrolithiasis. Because this clinical observation suggests a low-grade state of diffuse intravascular coagulation, standard clinical coagulation assays, platelet counts, and plasma fibrinopeptide A (FPA) levels were measured in patients before and during treatment with AHA. Coagulation assays, fibrinogen, and fibrin-split products were not significantly different when pretreatment and treatment values were compared. FPA levels were significantly elevated and platelet counts were significantly reduced in the treatment period, indicating augmented thrombin activity and consumption of platelets into thrombi or platelet microaggregates. FPA levels were elevated within 24 hours of the initiation of AHA therapy whereas platelet counts did not change significantly within the first 4 days of treatment. The data are consistent with low-grade intravascular coagulation with AHA treatment and suggest that patients treated with this agent should be observed cautiously for signs of thrombosis.

CT of fibrous tissues and tumors with sonographic correlation

Fibrous tissues and tumors may appear hyperdense relative to muscles and solid viscera on CT both before and after IV contrast injection. In addition, fibrous tissues generally have a homogeneously hypoechoic sonographic appearance. The diagnostic value of these criteria is illustrated in a group of 21 fibrous tissue abnormalities that includes retroperitoneal, mediastinal, and perigraft fibrosis, sclerosing pseudotumor of the orbit, generalized fibromatosis, desmoids, malignant fibrous histiocytoma, and normal tendons and ligaments. It is concluded that while hyperdensity on CT and echopenia on sonography are not pathognomonic of fibrous tissue, they occur with sufficient frequency that their presence raises the possibility of a fibrous lesion.

Interaction of prostaglandins, activated complement, and granulocytes in clinical sepsis and hypotension

Activated complement, thromboxane A2, prostacyclin, and activated granulocytes have been implicated in hemodynamic dysfunction after trauma, in sepsis, and in hypovolemic and septic shock. This study evaluated the interaction of plasma concentrations of complement components C3a and C5a, thromboxane B2 (TxB), prostaglandin 6-keto-F1 alpha (PGI), and granulocyte aggregation in clinical sepsis and hypotension. Forty-eight critically ill patients were followed clinically for as long as 10 days. Plasma C3a, C5a, TxB, and PGI were measured daily by the radioimmunoassay method. Granulocyte aggregation, the percentage of maximum aggregation of zymosan-activated plasma standard curves, was performed with patient plasma and normal human leukocytes. Patients were studied in four groups: group I, nonseptic, normotensive; group II, hypovolemic shock, group III, normotensive severe sepsis; and group IV, septic shock. Plasma from 12 normal adults was the control value. PGI, TxB, C3a, C5a, and granulocyte aggregation in patients were greater than that in the control subjects. Granulocyte aggregation was increased in groups III and IV versus groups I and II. C3a was increased in group IV versus groups II and III. C5a and TxB did not vary between groups. PGI was greatly increased in group IV compared with groups I through III. C3a and C5a decreased in nonsurvivors. PaO2/FiO2 ratios correlated directly with PGI and inversely with C3a and TxB/PGI. Plasma PGI and C3a are increased in septic shock. C3a and TxB/PGI imbalances are involved in hypovolemic and septic shock.

Influence of isoflurane on hypoxic pulmonary vasoconstriction in dogs

The authors studied the influence of locally administered isoflurane anesthesia on the pulmonary vascular response to regional alveolar hypoxia (hypoxic pulmonary vasoconstriction [HPV]) over a range of cardiac outputs (COs) in seven mechanically ventilated, closed-chest dogs. The right lung was ventilated with 100% O2 throughout the study. The left lung was ventilated with either 100% O2 (normoxia) or an hypoxic gas mixture (hypoxia). Different alveolar concentrations of isoflurane (0, 1, and 2.5 MAC) were administered to the left lung in a randomized sequence. The CO was altered by opening and closing surgically produced arteriovenous fistulae, at all isoflurane concentrations, and by hemorrhage at 0 MAC isoflurane. The magnitude of the HPV response was measured by differential CO2 elimination in the absence of isoflurane and by venous admixtures in all phases. During normoxia, the left lung effective flow (QL%) measured from differential CO2 excretion was 39.9 +/- 1.2% of the total blood flow and decreased to 18.8 +/- 2.6% when ventilated with the hypoxic gas mixture. Venous admixture (QVA/QT%) was significantly correlated with QL% during hypoxic ventilation in the absence of isoflurane. QVA/QT% was 22.3 +/- 2.7% during hypoxia with normal CO, and it increased significantly to 27.7 +/- 1.1% when the CO was increased 43%. It was not significantly altered (23.6 +/- 3.6%) when the CO was decreased by 54%. Isoflurane 2.5 MAC significantly increased QVA/QT% during hypoxic ventilation of the left lung to 33.9 +/- 2.6% with low CO and 35.4 +/- 1.7% with normal CO. Isoflurane 1 MAC increased QVA/QT% to 27.2 +/- 2.7% with normal CO and 28.1 +/- 2.6% with high CO.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin and complement interaction in clinical acute respiratory failure

This study investigated the interaction of plasma levels of circulating prostaglandins and activated complement in clinical acute respiratory failure (ARDS). Fifty patients at risk for ARDS were followed up for up to ten days. Arterial blood gases and plasma levels of complement components C3a and C5a, thromboxane B2 (TxB), and prostaglandin 6-keto-F1 alpha (PGI) and granulocyte aggregation (GA) were measured daily. Seventeen patients (34%) developed ARDS, with mortality of 41% vs 23% for patients without ARDS. Compared with patients without ARDS, the ARDS group had significantly increased plasma C3a (1,130 +/- 750 vs 636 +/- 368 ng/mL) and granulocyte aggregation (48 +/- 10 vs 17 +/- 4 percentage of the maximum light transmission [% max T]). Plasma C5a, TxB, or PGI did not change significantly with or without ARDS. No measured variable was significantly associated with mortality. Regression analysis revealed significant correlations between GA, TxB, PGI, and arterial oxygenation. Plasma C3a and GA are increased in ARDS, suggesting systemic complement activation. A complex series of interactions between the prostaglandins, complement, and GA appears to be involved in ARDS.

Leukocyte aggregation response to quantitative plasma levels of C3a and C5a

Granulocyte aggregation (GA) response has previously been described as a sensitive assay for complement activation in sepsis. Complement component C5a has been implicated as the plasma factor responsible for GA. The quantitative interaction of complement components C3a and C5a with GA, however, is not clearly defined. This study evaluates the relationship of GA responses to plasma levels of C5a and C3a in zymosan-activated plasma (ZAP). The C3a and C5a levels were measured by radioimmunoassay in serial dilutions of ZAP. Granulocyte aggregation responses of normal human leukocytes were determined for each ZAP dilution. The C5a levels in a 1:16 dilution of ZAP were higher than in normal plasma (22 +/- 7 vs 9 +/- 3 ng/mL), as were GA responses (24 +/- 1 vs 11 +/- 2 percentage of maximum light transmission). The C3a levels in a 1:8 dilution of ZAP are elevated above those of normal plasma (656 +/- 167 vs 411 +/- 29 ng/mL). Correlation coefficients were .9809 for C3a vs GA, .9788 for C5a vs G, and .9860 for C3a vs C5a. Complement components C3a and C5a are involved in GA in vitro. Granulocyte aggregometry can detect low levels of activated complement in ZAP but may not be specific for C5a. The relative contribution of C3a and C5a to observed GA is not clear from the data.

Hypoxic pulmonary vasoconstriction is not potentiated by repeated intermittent hypoxia in closed chest dogs

Hypoxic pulmonary vasoconstrictor (HPV) responses were measured with repeated intermittent hypoxic challenges in eight non-traumatized closed chest dogs anesthetized with pentobarbital. The right lung was ventilated continuously with 100% O2 while the left lung was either ventilated with 100% O2 (control) or ventilated with a gas mixture containing 3-4% O2 (hypoxia). Mean per cent left lung blood flow for all four normoxic periods was 43.1 +/- 1.5% (mean +/- SE) of the total blood flow by the SF6 excretion method and 40.8 +/- 1.1% by the differential CO2 excretion method, corrected for the Haldane effect. With hypoxic ventilation, flow diversion from the hypoxic lung was maximal with the first exposure and did not change subsequently with a total of four alternating exposures to normoxia and hypoxia. Flow diversion during hypoxia was approximately 50.5 +/- 2.4% by the SF6 method and 50.3 +/- 3.5% by the VCO2 method. This result contrasts with the increasing flow diversion response with intermittant hypoxic exposure that has been reported in animals exposed first to thoracotomy and surgical dissection. It is concluded that in the absence of surgical trauma the initial response to hypoxia is maximal and is not potentiated by repeated hypoxic stimulation.

Impact of renal donation. Long-term clinical and biochemical follow-up of living donors in a single center

Forty-six renal donors who responded to a questionnaire and two additional donors with nephrotic syndrome and renal insufficiency were studied. The mean age was 46 +/- 2.0 years (mean +/- SE). Duration of follow-up was 6 +/- 0.5 years. Serum creatinine levels increased from 1.0 +/- 0.03 mg/dl before donation to 1.2 +/- 0.04 mg/dl at follow-up. The incidence of proteinuria (more than 150 mg over 24 hours) was 39 percent. The serum creatinine level was 1.0 +/- 0.08 mg/dl and 1.2 +/- 0.06 mg/dl in the proteinuric and nonproteinuric groups, respectively. The incidence of hypertension was 31 percent with a serum creatinine level of 1.1 +/- 0.11 mg/dl and 1.2 +/- 0.07 mg/dl in the hypertensive and normotensive groups, respectively. One patient with nephrotic syndrome had proliferative glomerulonephritis. It is concluded that renal donation is associated with a minimal but statistically significant increment in serum creatinine levels. The incidence of mild hypertension and proteinuria is increased, but impact on renal function is minimal as assessed by serum creatinine determination.

The effect of dietary protein on cystine excretion in patients with cystinuria

Seven patients with homozygous cystinuria were studied on a metabolic ward to determine the effect of dietary manipulation on urinary cystine excretion. Isocaloric diets were calculated based on body weight and activity. Balance studies were performed for 5 days on a low protein diet (9.4 +/- 1.0% total calories) with equal amounts of animal and plant protein sources and an additional 5 days on a high protein (27 +/- 3.0% of total calories) with 70% animal protein. A significant (p less than 0.01) decrease in the excretion of 1/2-cystine, histidine, 3-methylhistidine, 1-methylhistidine, lysine, and ornithine plus arginine occurred on the low protein diet. The mean excretion of 1/2-cystine on the high protein diet was 6.13 +/- 1.48 mMoles per 24 hours which decreased to 4.89 +/- 1.06 mMoles per 24 hours on the low protein diet (p less than 0.001). Thirty seven percent of urine collections during the study were less than 2 liters/24 hours despite the fact that patients were encouraged to drink enough fluid to make 3 liters of urine/24 hours. For patients whose customary diet is high in animal protein, a more vegetarian diet may significantly reduce urinary cystine excretion. Cystine excretion in patients with cystinuria may be significantly different from day to day if animal protein consumption is variable.

A randomized double-blind study of acetohydroxamic acid in struvite nephrolithiasis

We studied the effects of the bacterial urease inhibitor acetohydroxamic acid on the growth of struvite stones in the urinary tract. Eighteen patients who received acetohydroxamic acid (15 mg per kilogram of body weight per day, in divided oral doses) for a mean of 15.8 months were compared in a randomized double-blind study with 19 patients who received placebo for a mean of 19.6 months. Seven patients given placebo reached a pre-determined end point: a 100 per cent increase in the two-dimensional surface area of their stones. No patient who received acetohydroxamic acid had a doubling of stone size (P less than 0.01). Nine patients receiving the drug and one patient receiving placebo required a decrease in dosage or cessation of treatment because of adverse effects (P less than 0.01). Episodes of tremulousness (n = 5, P less than 0.05), which reversed with a decrease in drug dose, and phlebothrombosis (n = 3, P not significant) were limited to the group given acetohydroxamic acid. We conclude that acetohydroxamic acid effectively inhibits the growth of struvite stones in the short term in patients infected with urea-splitting bacteria, but the prevalence of adverse reactions appears to be high and the toxicity and effectiveness of long-term therapy for struvite nephrolithiasis remain to be defined.

CT of the hyperdense renal cyst: sonographic correlation

The computed tomographic (CT) appearances of 19 hyperdense renal cysts in nine patients are reported. Sixteen of these cysts were found over a period of only 1 year with state-of-the-art CT equipment. Hyperdense renal cysts are probably more common than suggested by case reports. Their rate of detection can be expected to increase with the wider availability of fast CT scanners using thin collimation. A CT diagnosis of benign hyperdense renal cyst can be made if a lesion meets all of the following criteria: (1) smoothly outlined imperceptible wall with sharp demarcation from the kidney; (2) before intravenous contrast injection, homogeneous internal content with CT numbers 40%-240% higher (70%-240% higher for lesions 10 mm or more in diameter) than renal parenchyma; and (3) after intravenous contrast injection, persistent internal homogeneity and insignificant enhancement (less than 6%) relative to normal renal cortex. For masses exceeding 15 mm in diameter, sonography can be a valuable confirmatory test.

Time course and responses of sustained hypoxic pulmonary vasoconstriction in the dog

The stability of the pulmonary blood pressure and flow response to alveolar hypoxia (hypoxic pulmonary vasoconstriction or HPV) was studied in six pentobarbital anesthetized, mechanically ventilated open-chested dogs. Aortic and left pulmonary artery blood flows; systemic and pulmonary arterial, central venous, left atrial, and airway pressures; hemoglobin; arterial and mixed venous blood gases were measured. The right lung was ventilated continuously with 100% oxygen, while the left lung was ventilated alternately with 100% O2 ( prehypoxia control phase), an hypoxic gas mixture containing 4% O2, 3% CO2, balance N2 for 4 h, or 100% O2 (post-hypoxia control phase). Hypoxic ventilation of the left lung resulted in an immediate and sustained decrease in left lung blood flow (QL%) from 39.0 +/- 1.8% (mean +/- SE) to 9.9 +/- 3.6% at 15 min of hypoxic ventilation. QL% remained decreased and did not vary significantly during the 4 h of hypoxia. Venous admixture correspondingly was increased and PaO2 decreased by hypoxic ventilation and did not vary significantly during the 4 h of hypoxia. All variables returned to control levels upon reestablishing ventilation with 100% O2. While the maximal reduction in QL% with left lung hypoxic ventilation was identical to that observed during atelectasis previously in our laboratory, the time course of the response was different. The response to hypoxia was maximal by 15 min, however, QL% decreased more slowly during atelectasis, where the maximal reduction was observed by 60 min. The present study therefore demonstrated that hypoxic ventilation of the left lung yielded an immediate and sustained decrease in left lung blood flow for 4 h. The stability of the HPV response probably was accounted for by the lack of such confounding factors as respiratory alkalosis, severe systemic hypoxemia, and increased cardiac output.