Withdrawal during outpatient low dose buprenorphine initiation in people who use fentanyl: a retrospective cohort study

BACKGROUND

Buprenorphine is an effective treatment for opioid use disorder (OUD); however, buprenorphine initiation can be complicated by withdrawal symptoms including precipitated withdrawal. There has been increasing interest in using low dose initiation (LDI) strategies to reduce this withdrawal risk. As there are limited data on withdrawal symptoms during LDI, we characterize withdrawal symptoms in people with daily fentanyl use who underwent initiation using these strategies as outpatients.

METHODS

We conducted a retrospective chart review of patients with OUD using daily fentanyl who were prescribed 7-day or 4-day LDI at 2 substance use disorder treatment clinics in San Francisco. Two addiction medicine experts assessed extracted chart documentation for withdrawal severity and precipitated withdrawal, defined as acute worsening of withdrawal symptoms immediately after taking buprenorphine. A third expert adjudicated disagreements. Data were analyzed using descriptive statistics.

RESULTS

There were 175 initiations in 126 patients. The mean age was 37 (SD 10 years). 71% were men, 26% women, and 2% non-binary. 21% identified as Black, 16% Latine, and 52% white. 60% were unstably housed and 75% had Medicaid insurance. Substance co-use included 74% who used amphetamines, 29% cocaine, 22% benzodiazepines, and 19% alcohol. Follow up was available for 118 (67%) initiations. There was deviation from protocol instructions in 22% of these initiations with follow up. 31% had any withdrawal, including 21% with mild symptoms, 8% moderate and 2% severe. Precipitated withdrawal occurred in 10 cases, or 8% of initiations with follow up. Of these, 7 had deviation from protocol instructions; thus, there were 3 cases with follow up (3%) in which precipitated withdrawal occurred without protocol deviation.

CONCLUSIONS

Withdrawal was relatively common in our cohort but was mostly mild, and precipitated withdrawal was rare. Deviation from instructions, structural barriers, and varying fentanyl use characteristics may contribute to withdrawal. Clinicians should counsel patients who use fentanyl that mild withdrawal symptoms are likely during LDI, and there is still a low risk for precipitated withdrawal. Future studies should compare withdrawal across initiation types, seek ways to support patients in initiating buprenorphine, and qualitatively elicit patients' withdrawal experiences.

The Howard Street Method: A Community Pharmacy-led Low Dose Overlap Buprenorphine Initiation Protocol for Individuals Using Fentanyl

OBJECTIVES

Buprenorphine treatment significantly reduces morbidity and mortality for people with opioid use disorder. Fear of precipitated withdrawal remains a barrier to starting buprenorphine for patients who use synthetic opioids, particularly fentanyl. We aim to evaluate the development and implementation of a buprenorphine low dose overlap initiation (LDOI) protocol in an urban public health community pharmacy.

METHODS

We performed a retrospective chart review of patients with nonprescribed fentanyl use (N = 27) to examine clinical outcomes of a buprenorphine LDOI schedule, named the Howard Street Method, dispensed from a community pharmacy in San Francisco from January to December 2020.

RESULTS

Twenty-seven patients were prescribed the Howard Street Method. Twenty-six patients picked up the prescription and 14 completed the protocol. Of those who completed the protocol, 11 (79%) reported no symptoms of withdrawal and 3 (21%) reported mild symptoms. Four patients (29%) reported cessation of full opioid agonist use and 10 (71%) reported reduction in their use by the end of the protocol. At 30 days, 12 patients (86%) were retained in care and 10 (71%) continued buprenorphine. At 180 days, 6 patients (43%) were retained in care and 2 (14%) were still receiving buprenorphine treatment.

CONCLUSIONS

We found that a LDOI blister-pack protocol based at a community pharmacy was a viable intervention for starting buprenorphine treatment and a promising alternative method for buprenorphine initiation in an underresourced, safety-net population of people using fentanyl.

Rapid Overlap Initiation Protocol Using Low Dose Buprenorphine for Opioid Use Disorder Treatment in an Outpatient Setting: A Case Series

OBJECTIVES

Fear and risk of precipitated withdrawal are barriers for initiating buprenorphine in individuals with opioid use disorder, particularly among those using fentanyl. A buprenorphine rapid overlap initiation (ROI) protocol (also knownas "rapidmicro-dosing") utilizing small, escalating doses of buprenorphine can overcome this barrier, reaching therapeutic doses in 3 to 4 days. We sought to demonstrate the feasibility of implementing a buprenorphine ROI protocol for buprenorphine initiation in the outpatient setting.

METHODS

We conducted a retrospective chart review of patients prescribed an outpatient ROI protocol at the Office-based Buprenorphine Induction Clinic from October to December 2020. The ROI protocol utilizes divided doses of sublingual buprenorphine tablets and blister packaging for easier dosing. Patients were not required to stop other opioid use and were advised to follow up on day 4 of initiation.

RESULTS

Twelve patients were included, of whom eleven (92%) were using fentanyl at intake. Eleven patients picked up their prescription. Seven patients returned for follow-up (58%), and all 7 completed the ROI protocol. One patient reported any withdrawal symptoms, which were mild. At 30 days, 7 patients (58%) were retained in care, and 5 (42%) were still receiving buprenorphine treatment, 4 (33%) of whom had been abstinent from nonprescribed opioid use for ≥2 weeks.

CONCLUSIONS

The ROI protocol was successful in initiating buprenorphine treatment for patients in our outpatient clinic, many of whom were using fentanyl. The ROI protocol may offer a safe alternative to traditional buprenorphine initiation and warrants further study.

Coherent Electron Optics with Ballistically Coupled Quantum Point Contacts

The realization of integrated quantum circuits requires precise on-chip control of charge carriers. Aiming at the coherent coupling of distant nanostructures at zero magnetic field, here we study the ballistic electron transport through two quantum point contacts (QPCs) in series in a three terminal configuration. We enhance the coupling between the QPCs by electrostatic focusing using a field effect lens. To study the emission and collection properties of QPCs in detail we combine the electrostatic focusing with magnetic deflection. Comparing our measurements with quantum mechanical and classical calculations we discuss generic features of the quantum circuit and demonstrate how the coherent and ballistic dynamics depend on the details of the QPC confinement potentials.

Acceptability of Naloxone Dispensing Among Pharmacists

BACKGROUND

The San Francisco Department of Public Health initiated naloxone prescribing at 6 safety net clinics. We evaluated this intervention, demonstrating that naloxone prescribing from primary care clinics is feasible and acceptable.

OBJECTIVE

To evaluate acceptability of naloxone dispensing to patients prescribed opioids among pharmacists serving clinics participating in a naloxone intervention.

METHODS

We surveyed 58 pharmacists from November 2013 through January 2015 at pharmacies that serviced San Francisco safety net clinics. Surveys collected information on demographics, experiences in dispensing naloxone, and interest in prescriptive authority. We conducted descriptive analyses and assessed bivariate relationships.

RESULTS

Most respondents were staff (56.9%) or supervising pharmacists (34.5%). Most (92.9%) were aware their pharmacy stocked naloxone and 86.8% felt it should be prescribed to some or all patients on long-term opioids. Most (82.1%) dispensed naloxone at least once in the past 12 months. More than half were comfortable providing naloxone education. Nearly half (43.4%) indicated they would want authority to furnish without a prescription. Over half (55.2%) reported no problems dispensing. The common problem was insufficient naloxone knowledge. Only 12% reported more than one problem in dispensing naloxone, which was associated with being uncomfortable with educating patients (P = .03).

CONCLUSION

Naloxone dispensing was acceptable among pharmacists. Their most cited problem was insufficient naloxone education. This may be resolved with improved instructional materials, incentives for patient education, or mandatory training.

Feasibility of radiotherapy in nonagenarian patients: a retrospective study

PURPOSE

Specific information about radiation therapy in nonagenarians is limited. In order to shed more light on the feasibility of radiotherapy in this challenging subgroup, a retrospective study was performed.

METHODS

The data of 93 consecutive patients receiving irradiation treatment at the Department of Radiation Oncology, Ordensklinikum Linz Barmherzige Schwestern between June 2005 and December 2016 were analyzed. Patient- and treatment-related factors were extracted from the patient records. Overall survival (OS) was defined as time from irradiation to death or last follow-up. The survival rates were analyzed using the Kaplan-Meier method and log-rank test.

RESULTS

The study population of 93 patients was between 90 and 99 years old (median 91 years). It included 59 women (63%) and 34 men (37%). Of these, 38 (41%) received definitive radiotherapy, 14 (15%) received neoadjuvant or adjuvant radiotherapy, whereas a palliative regimen was prescribed in 44% of the cases (n = 41). In all, 79 patients (85%) were able to complete their prescribed course of radiotherapy. While 16 (17%) patients reported grade 2 toxicities or higher, 4 had ≥grade 3 side effects (4%). The median survival was significantly higher in patients treated with adjuvant, neoadjuvant or definitive radiotherapy (13.8 months) compared to patients treated with palliative radiotherapy (3.6 months; p < 0.001).

CONCLUSION

Even in patients managed without preradiotherapy comprehensive geriatric assessment, carefully planned fractionated radiotherapy was feasible and resulted in acceptable rates of acute toxicities.

Evaluation of the Impact of a Multimodel Intervention on Prescribing Patterns of Sedative-Hypnotics in a Behavioral Health System

Objective

To describe the effect of a multimodal intervention targeting chronic benzodiazepine and sedative-hypnotic prescriptions in a large behavioral health system.

Methods

This retrospective study analyzed chronic sedative-hypnotic prescription rates in patients seeking mental health services in a large behavioral health system. The multimodal intervention consisted of provider education, coordination of care with all providers involved in patient care, and guideline development and implementation for safe prescribing of sedative-hypnotics. Three time periods were analyzed: preintervention (October 2013-December 2013), 12-month assessment (October 2014-December 2014), and 24-month assessment (October 2015-December 2015). The primary outcome of the study was the change in frequency of chronic (≥ 60 days) sedative-hypnotic prescriptions received before and after the multimodal intervention. The secondary outcome included the change in prescription rates in a priori-defined cohorts: patients on methadone maintenance therapy and patients ≥ 60 years of age.

Results

There were 32,944 prescriptions during the study period. The rate of chronic sedative-hypnotic prescriptions decreased from 1,764 (15.3%) to 1,634 (14.9%) to 1,018 (9.8%) between the 3 assessment periods, respectively. A significant decrease occurred between the preintervention period and 24-month assessment (5.5%, P < .0001) and between the 12-month assessment and the 24-month assessment (5.1%, P < .0001). In the elderly, prescription rates decreased significantly between the preintervention period and the 24-month assessment (3.6%, P < .0001) and the 12-month and 24-month assessments (3.2%, P = .0001). In patients in methadone maintenance programs, rates of concomitant chronic sedative-hypnotic prescriptions decreased significantly between all assessment periods: preintervention and 12-month assessment (8.2%, P = .001), 12-month and 24-month assessment (6.3%, P = .002), and preintervention and 24-month assessment (14.5%, P < .0001). Additionally, prescription rates increased significantly for antidepressants (4.1%, P < .05), hydroxyzine (1.1%, P = .01), buspirone (2.1%, P < .05), gabapentin (6.3%, P < .05), and melatonin agonists (0.3%, P < .05) between the preintervention and 24-month assessment periods.

Conclusions

Implementation of a multimodal intervention led to a significant decrease in rates of chronic sedative-hypnotic prescriptions in a large behavioral health system.

Intolerance of sublingual buprenorphine-naloxone during induction in a patient with end-stage liver disease: A case report

Introduction

Sublingual buprenorphine is indicated for opioid dependence. It comes in 2 formulations: a mono buprenorphine product (BUP) and a combination product containing naloxone (BUP-NAL), which functions as an abuse deterrent. Sublingual naloxone does not reach clinically significant levels except in cases of hepatic impairment, where its metabolism can be impaired. Substantial naloxone accumulation could block the therapeutic effects of buprenorphine. The risk of hepatic impairment is elevated in the opioid dependence population, and our case highlights the need for careful evaluation of hepatic function and consideration of BUP.

Case/Results

We report a patient with end-stage liver disease who began BUP-NAL induction with modest improvement on treatment day 1 followed by sustained withdrawal after receiving an observed dose on day 2. He returned to the clinic 2 days after his second successive day of BUP-NAL, vomiting and complaining of persistent withdrawal. To avoid potential accumulation of naloxone, the patient was eventually switched to and stabilized on BUP with good response.

Discussion/Conclusion

The clinical course this patient experienced during induction makes a case that naloxone can accumulate and interfere with the effectiveness of buprenorphine in the presence of liver dysfunction. Our case highlights the need for consideration of BUP in circumstances where patient safety and effective treatment outweigh the risks of prescribing a product with abuse deterrent properties.

Naloxone prescribing by psychiatric clinical pharmacists for patients receiving opioid agonist treatment

Take-home naloxone is an important intervention for addressing opioid overdoses. Patients with a history of a substance use disorder are at an elevated risk of experiencing an overdose, and even in substance-abuse treatment, they may continue to witness peer overdoses. The purpose of this innovative practice was for psychiatric clinical pharmacists to improve access to intranasal naloxone and provide opioid overdose prevention training for patients receiving opioid agonist treatment (OAT). This program took place at a San Francisco Department of Public Health pharmacy that provides OAT (buprenorphine and methadone) to approximately 200 patients with opioid use disorders as part of an integrated treatment program. During the 17-month study period, 47 intranasal naloxone kits were prescribed. Patients reported 3 successful opioid overdose reversals using intranasal naloxone. Based on these findings, psychiatric clinical pharmacists can improve patient safety by increasing access to intranasal naloxone and opioid overdose prevention training for patients receiving OAT.

Evaluation of the effectiveness of mass trapping with BG-sentinel traps for dengue vector control: a cluster randomized controlled trial in Manaus, Brazil

The objective of this study was to assess the effectiveness of BG-Sentinel (BGS) traps for mass trapping at the household level to control the dengue vector, Aedes aegypti (L.), in Manaus (Brazil) by performing a cluster randomized controlled trial. After an initial questionnaire and baseline monitoring, 6 out of 12 clusters were randomly allocated to the intervention arm, where participating premises received one BGS trap for mass trapping. The other six clusters did not receive traps and were considered as the control arm. Biweekly monitoring with BGS in both arms assessed the impact of mass trapping. At the end of the study, a serological survey was conducted and a second questionnaire was conducted in the intervention arm. Entomological monitoring indicated that mass trapping with BGS traps significantly reduced the abundance of adult female Ae. aegypti during the first five rainy months. In the subsequent dry season when the mosquito population was lower, no effect of mass trapping was observed. Fewer Ae. aegypti females were measured in the intervention arm during the next rainy period, but no significant difference between arms was observed. The serological survey revealed that in participating houses of mass trapping areas recent dengue infections were less common than in control areas, although this effect was not statistically significant. The majority of participants responded positively to questions concerning user satisfaction. Our results suggest that BGS traps are a promising tool which might be deployed as part of dengue control programs; however, further investigations and larger scale studies are necessary.

Laboratory evaluation techniques to investigate the spatial potential of repellents for push and pull mosquito control systems

A protocol has been developed for the indoor evaluation of candidate spatial repellents intended for use in push and pull systems. Single treatments (catnip oil, 1-methylpiperazine, and homopiperazine) and a mixture of catnip oil and homopiperazine were tested with yellow-fever mosquitoes (Aedes aegypti) in Y-tube olfactometers to determine 1) if these compounds inhibited mosquito host-seeking at short distances and 2) if results obtained in olfactometer tests can be correlated with a larger scale set-up, that is, a room test. All test materials significantly decreased the ability of mosquitoes to find host odors (from a human finger) by up to 96.7% (2.5% catnip and homopiperazine mix). Similar effects could be observed within a new room test set-up, which involved a repellent dispensing system and an attractive trap (BG-Sentinel). Mosquitoes captured by the BGS trap had to fly through a treatment-containing air curtain created by the dispensing system. Compared with the use of a control (ethanol solvent without candidate repellent), trap catch rates were significantly reduced when 5% catnip, 5% 1-methylpiperazine, and 5% homopiperazine were dispensed. Homopiperazine produced the greatest level of host-seeking inhibition with a 95% reduction in the trap catches. The experimental set-up was modified to test the viability of those technologies in a simple push & pull situation.. The combination of BGS trap and a 10% mix of catnip and homopiperazine helped to reduce human landing rates by up to 44.2% with a volunteer sitting behind the air curtain and the trap running in front of the curtain.

Lithium as augmentation for major depressive disorder

Although lithium does not have an FDA approved indication for augmentation of an antidepressant in major depressive disorder, it has been prescribed for this purpose for decades. While a wide variety of medications have been used historically in this capacity, lithium is one of the few agents that has demonstrated efficacy in multiple randomized controlled trials. Although the ideal role for lithium augmentation has yet to be established, there is currently ample evidence to support the clinical practice of adding lithium to conventional antidepressants in pursuit of major depressive disorder remission.

Dose-escalated simultaneous integrated-boost treatment of prostate cancer patients via helical tomotherapy

PURPOSE

The goal of this work was to assess the feasibility of moderately hypofractionated simultaneous integrated-boost intensity-modulated radiotherapy (SIB-IMRT) with helical tomotherapy in patients with localized prostate cancer regarding acute side effects and dose-volume histogram data (DVH data).

METHODS

Acute side effects and DVH data were evaluated of the first 40 intermediate risk prostate cancer patients treated with a definitive daily image-guided SIB-IMRT protocol via helical tomotherapy in our department. The planning target volume including the prostate and the base of the seminal vesicles with safety margins was treated with 70 Gy in 35 fractions. The boost volume containing the prostate and 3 mm safety margins (5 mm craniocaudal) was treated as SIB to a total dose of 76 Gy (2.17 Gy per fraction). Planning constraints for the anterior rectal wall were set in order not to exceed the dose of 76 Gy prescribed to the boost volume. Acute toxicity was evaluated prospectively using a modified CTCAE (Common Terminology Criteria for Adverse Events) score.

RESULTS

SIB-IMRT allowed good rectal sparing, although the full boost dose was permitted to the anterior rectal wall. Median rectum dose was 38 Gy in all patients and the median volumes receiving at least 65 Gy (V65), 70 Gy (V70), and 75 Gy (V75) were 13.5%, 9%, and 3%, respectively. No grade 4 toxicity was observed. Acute grade 3 toxicity was observed in 20% of patients involving nocturia only. Grade 2 acute intestinal and urological side effects occurred in 25% and 57.5%, respectively. No correlation was found between acute toxicity and the DVH data.

CONCLUSION

This institutional SIB-IMRT protocol using daily image guidance as a precondition for smaller safety margins allows dose escalation to the prostate without increasing acute toxicity.

A novel test cage with an air ventilation system as an alternative to conventional cages for the efficacy testing of mosquito repellents

We have developed a novel test cage and improved method for the evaluation of mosquito repellents. The method is compatible with the United States Environmental Protection Agency, 2000 draft OPPTS 810.3700 Product Performance Test Guidelines for Testing of Insect Repellents. The Biogents cages (BG-cages) require fewer test mosquitoes than conventional cages and are more comfortable for the human volunteers. The novel cage allows a section of treated forearm from a volunteer to be exposed to mosquito probing through a window. This design minimizes residual contamination of cage surfaces with repellent. In addition, an air ventilation system supplies conditioned air to the cages after each single test, to flush out and prevent any accumulation of test substances. During biting activity tests, the untreated skin surface does not receive bites because of a screen placed 150 mm above the skin. Compared with the OPPTS 810.3700 method, the BG-cage is smaller (27 liters, compared with 56 liters) and contains 30 rather than hundreds of blood-hungry female mosquitoes. We compared the performance of a proprietary repellent formulation containing 20% KBR3023 with four volunteers on Aedes aegypti (L.) (Diptera: Culicidae) in BG- and conventional cages. Repellent protection time was shorter in tests conducted with conventional cages. The average 95% protection time was 4.5 +/- 0.4 h in conventional cages and 7.5 +/- 0.6 h in the novel BG-cages. The protection times measured in BG-cages were more similar to the protection times determined with these repellents in field tests.

A search for components in human body odour that attract females of Aedes aegypti

In a new type of wind tunnel, mosquitoes fly upwind towards host odour sources and towards human skin wash extracts obtained by rubbing the skin with a pad soaked in ethanol. We used this behavioural response as a bioassay to identify attractants in liquid chromatography fractions of such extracts. L-Lactic acid is a major constituent of skin wash extracts and it is a necessary component for the extract's effectiveness. As a single stimulus, however, L-lactic acid is only slightly effective. This indicates that the extract's high degree of effectiveness is based on a synergism of L-lactic acid and other odour components. The separation of the extract by liquid chromatography revealed three distinct regions of active fractions, only one of which contained L-lactic acid. The components of the other two regions have not yet been determined. A combination of fractions in these two regions together with L-lactic acid is as attractive as the complete extract.

Responses of antennal olfactory receptors in the yellow fever mosquito Aedes aegypti to human body odours

Recent behavioural studies have demonstrated that human body odours which female Aedes aegypti find attractive exert their effects as complex mixtures of synergistically acting components. We have attempted to clarify the sensory mechanisms underlying the perception of these complex host odours by studying the responses of sensory cells underneath the A3-type sensilla of the mosquito antenna to both a human skin wash extract and the extract's active chromatographic fractions. The reaction patterns show that the host stimuli elicit responses from several types of receptor cells in a typical across-fibre pattern mode. It seems as if this is another case where the essential message in a biologically significant odour consists of a complex pattern of compounds that is encoded in an according complex response pattern by a cooperating set of primary sensory neurons of different odour specificities.

L-lactic acid: a human-signifying host cue for the anthropophilic mosquito Anopheles gambiae

Using a dual-choice olfactometer, the role of L-lactic acid was investigated in relation to host-seeking and selection by female Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) mosquitoes in a Y-tube bioassay. L-lactic acid alone was not attractive, but it significantly augmented the attractiveness of CO2, skin odour and skin-rubbing extracts from humans and other vertebrates. Comparing the left and right index fingers of the same person, one could be made more attractive than the other by adding L-lactic acid to the air stream over that finger. The difference in L-lactic acid concentration between the two air streams offered to the mosquitoes fell within the natural range of variation emanating from a human hand, suggesting that L-lactic acid modulates intraspecific host selection by An. gambiae. Analysis of skin rubbings from various vertebrates (carnivores, chickens, primates, rodents, ungulates) indicated that humans have uniquely high levels of L-lactic acid on their skin. Tests with extracts of skin rubbings from cows and humans, with and without added L-lactic acid, suggest that naturally lower levels of L-lactic acid contribute to the lesser attractiveness of non-humans to An. gambiae s.s.

The effect of lactic acid on odour-related host preference of yellow fever mosquitoes

In a behavioural study we have investigated the role of lactic acid for the host preferences of yellow fever mosquitoes (Aedes aegypti) by comparing the attractiveness of rubbings from the hands of different human individuals and extracts obtained from skin rubbings from different mammals (Bos primigenius f. taurus, Capra aegagrus f. hircus, Felis silvestris f. catus and Homo sapiens). Certain human individuals were consistently more attractive to mosquitoes than others. Addition of lactic acid markedly increased the degree of attractiveness of formerly less attractive human odour samples and they were preferred over those which were originally the most attractive. There was almost no response to animal odour samples. In contrast to human samples, which contain a high amount of lactate, this compound could not be detected in samples from animals. When skin emanations from animals were combined with lactic acid, however, as many mosquitoes responded to odour samples of B. primigenius f. taurus and C. aegagrus f. hircus as did to human odours. All these data demonstrate that olfactory-based host preference of the anthropophilic mosquito A. aegypti is to a large extent due to differences in the amount of lactic acid in the odour samples.

An easy and accurate agarose gel assay for quantitation of bacterial plasmid copy numbers

An assay for quantitation of plasmid copy numbers in bacterial cell cultures has been developed and validated. The method combines isolation of total bacterial DNA (including both plasmid and genomic DNA), running a series of twofold dilutions of total DNA in an agarose gel followed by ethidium bromide staining, and subsequent scanning of the gel picture negatives. We have developed a novel set of rules for integration of the scan data that allows us to achieve high assay precision, accuracy, and sensitivity. The assay validation results were as follows: intra- and interassay precision with %CV of 8.2-9.9 and 7.1-9.8%, respectively; ruggedness with %CV of 9.3-17.5%; spike recovery of 80-102%; and sensitivity of 1 plasmid copy per genome.

Contribution of fatty acids to olfactory host finding of female Aedes aegypti

Single carbon to 18 carbon n-aliphatic carboxylic acids were tested for their attractive effects on female Aedes aegypti in a Y-tube olfactometer. Each acid was tested over a wide range of concentrations together with L-(+)-lactic acid, the indispensable synergist for other attractive components emitted from human hosts. The attractiveness of lactic acid was significantly augmented when combined with fatty acids of chain length C(1)-C(3), C(5)-C(8) and C(13)-C(18), respectively. The addition of the C(9) and C(11) acids reduced the attractive effect of lactic acid. According to experiments showing a further increase of attractiveness by adding a second fatty acid, we suggest two groups of attractive carboxylic acids: C(1)-C(3) and C(5)-C(8). The addition of a fatty acid from one group to a mixture of lactic acid and an acid from the other group augmented the attraction to the mixture. Together with ammonia, a previously demonstrated attractant for Aedes aegypti, lactic acid plus two fatty acids from the different groups formed the hitherto most attractive, artificially composed blend. Two of the carboxylic acids which were found to be attractive together with lactic acid were also tested alone and in combination with CO(2), the major attractant in human breath. In both cases no attractive effect of the carboxylic acids could be observed.

Ammonia as an attractive component of host odour for the yellow fever mosquito, Aedes aegypti

Behavioural responses of Aedes aegypti mosquitoes to ammonia were investigated in a modified Y-tube olfactometer. Ammonia was attractive in concentrations from 17 ppb to 17 ppm in air when presented together with lactic acid. Aqueous solutions of ammonia salts in concentrations comparable to those found in human sweat also increased the attractiveness of lactic acid. The role of lactic acid as an essential synergist for ammonia became further apparent by the fact that ammonia alone or in combination with carbon dioxide was not effective, even though the synergistic effect of carbon dioxide and lactic acid was corroborated. An extract from human skin residues, which attracts approximately 80% of the tested mosquitoes, contains both lactic acid and ammonia. The combination of these compounds, however, attracts no more than 45%, indicating that other components on human skin also play a role in host finding. Preparative liquid chromatography of the skin extract yielded three behaviourally active fractions which work together synergistically. Fraction III contains lactic acid as the effective principle; the compositions of the other two have not been clarified yet. The attractiveness of fraction I was augmented considerably when ammonia was added, whereas the effect of fraction II was not influenced by ammonia. These results suggests that ammonia is part of the effective principle of fraction II and contributes to the attractive effect of host odours.

Influence of odour plume structure on upwind flight of mosquitoes towards hosts

Both the concentration and the fine-scale plume structure of host odours influence the upwind flight of female mosquitoes Aedes aegypti (L.) (Diptera: Culicidae) in a wind tunnel. The attractive effects of carbon dioxide, human skin odour and l-(+)-lactic acid were tested in homogeneous, turbulent and filamentous odour plumes. With carbon dioxide, the percentage of upwind-flying mosquitoes increased with the increasing fluctuations in concentration that occur in turbulent and filamentous plumes. In homogeneous plumes, an initial activation effect was observed, but sustained upwind flights were less frequent than in the other plumes. The opposite was found with plumes of human skin odour: the highest number of mosquitoes flew upwind in the homogeneous plume, whereas in turbulent or filamentous plumes their numbers were significantly lower. Regardless of plume type, the percentage of upwind-flying mosquitoes increased with increasing concentrations of carbon dioxide and of skin odour. With l-(+)-lactic acid, the dose-response characteristics were not consistent, and the relative effects of different plume types upon upwind flights differed within different ranges of concentration. Even maximum reactions to this compound were modest compared with those to carbon dioxide or to skin odour. Our findings demonstrate (1) that mosquitoes are able to orient upwind under continuous odour stimulation and (2) that upwind flight is dependent upon plume structure in different ways for different host odour components.

[Control system for a complete artificial heart based on a mean value model of the cardiovascular system]

The reliable use of an artificial heart in patients requires a control strategy that is able to monitor and realistically regulate the different loads of the cardiovascular system. The model outlined in the following article was created in an interdisciplinary environment with heart specialists and automation engineers. A control system for an artificial heart, in the form of a peristaltic pump, was created with the help of a load-dependent mean-value model of the cardiovascular system. The resistance of the arterioles in the systemic vascular system RA was chosen as the parameter for the adaptation of the cardiac output. This parameters can be easily and accurately estimated through the measurement of pressures and flows, and it is a very good indicator for the load of the organism. The results, obtained through simulation of the overall system, show a very fast and accurate adaptation of the cardiac output to the needs of the body at changing loads over a large range of workloads. At the same time, the protection of the lungs from excessive pressure is ensured by balance control of the outputs of the two halves of the artificial heart. The control system outlined here needs only pressure and flow sensors, which can be integrated into the pump housing.

Accumulation of colony-stimulating factor 1 in amniotic fluid during human pregnancy

Colony-stimulating factor 1 is a hematopoietic growth factor that increases 1000-fold in the uteri of pregnant mice, and its receptor is abundantly expressed in the human placenta. The concentration of colony-stimulating factor 1 in amniotic fluid at 33 to 40 weeks (9.0 +/- 1.1 ng/ml) was twofold higher than that at 16 to 18 weeks gestation (4.1 +/- 0.5 ng/ml), whereas maternal serum colony-stimulating factor 1 levels did not rise significantly. Colony-stimulating factor 1 was detected in endometrial extracts from pregnant women and levels were higher than those in extracts from nonpregnant women.