Experience with the Jostra Rotaflow and QuadroxD oxygenator for ECMO

Since April 1988, we have been able to offer extracorporeal membrane oxygenation (ECMO) to patients who are either failing ventilation or who need cardiopulmonary support following cardiac surgery. During this time, we have supported 211 patients, the majority of whom have been supported with the Avecor (Affinity, Avecor Cardiovascular Inc., Minneapolis, MN, USA) spiral wound silicone-membrane oxygenator. Microporous hollow-fibre oxygenators have been used (18%) at our center. However, due to their early failure, they have necessitated conversion to a device that potentially would last for the entire ECMO course, i.e., Avecor and, subsequently, have not been used routinely until the introduction of the QuadroxD (Jostra Medizintechnik AG, Hirrlingen, Germany). The recent development of the poly-4-methyl-1-pentene diffusion membrane allows us to utilize hollow-fibre technology with a true (nonmicroporous) membrane. This has enabled us to use this low-resistance device with all its inherent advantages, without plasma leakage necessitating circuit changeover. From July 2000, we have used the QuadroxD oxygenator for our patients requiring ECMO support. This has been in patients with weights ranging from 2.16-51.0 kg ( n = 23), with the longest support being for 1119 hours. This new technology has enabled us to utilize a single device for all patient sizes, so we now have an ECMO circuit set up at all times, minimizing the time required for support to be available, potentially improving survivor morbidity.

Pump-induced haemolysis: a comparison of short-term ventricular assist devices

Centrifugal pumps are superior to roller pumps for extended support durations in terms of pump-induced haemolysis. In this study, we evaluated the commonly used Biomedicus BP 50 and compared it with the Jostra Rotaflow and a standard roller pump in an in vitro test circuit. Each circuit was run for a six-day period and repeated five times. Plasma haemoglobin values showed the roller pump to become more haemolytic than the Biomedicus ( p = 0.022) and the Rotaflow. A statistically significant difference between the Biomedicus and the Rotaflow was observed on day six of the trial ( p = 0.016), with the Rotaflow showing lower levels of haemolysis than the Biomedicus. These results support the use of the new generation centrifugal pump, the Rotaflow, as a suitable device for short-term ventricular assist.

A Review of Paclitaxel and Novel Formulations Including Those Suitable for Use in Dogs

Paclitaxel is a commonly used chemotherapeutic agent with a broad spectrum of activity against cancers in humans. In 1992, paclitaxel was approved by the U.S. Food and Drug Administration (FDA) as Taxol(®) for use in advanced ovarian cancer. Two years later, it was approved for the treatment of metastatic breast cancer. Paclitaxel was originally isolated from the bark of the Pacific yew tree, Taxus brevifolia in 1971. Taxanes are a family of microtubule inhibitors. As a member of this family, paclitaxel suppresses spindle microtubule dynamics. This activity results in the blockage of the metaphase-anaphase transitions, and ultimately in the inhibition of mitosis, and induction of apoptosis in a wide spectrum of cancer cells. Additional anticancer activities of paclitaxel have been defined that are independent of these effects on the microtubules and may include the suppression of cell proliferation as well as antiangiogenic effects. Based on its targeting of a fundamental feature of the cancer phenotype, the mitotic complex, it is not surprising that paclitaxel has been found to be active in a wide variety of cancers in humans. This review summarizes the evidence in support of paclitaxel's broad anticancer activity and introduces the rationale for, and the progress in development of novel formulations of paclitaxel that may preferentially target cancers and that are not associated with the risks for hypersensitivity in dogs. Of note, a novel nanoparticle formulation of paclitaxel that substantially limits hypersensitivity was recently given conditional approval by the FDA Center for Veterinary Medicine for use in dogs with resectable and nonresectable squamous cell carcinoma and nonresectable stage III, IV and V mammary carcinoma.

The International Association for the Study of Lung Cancer Lung Cancer Staging Project: Proposals for the Revision of the Clinical and Pathologic Staging of Small Cell Lung Cancer in the Forthcoming Eighth Edition of the TNM Classification for Lung Cancer

INTRODUCTION

Small cell lung cancer (SCLC) is commonly classified as either limited or extensive, but the Union for International Cancer Control TNM Classification of Malignant Tumours seventh edition (2009) recommended tumor, node, and metastasis (TNM) staging based on analysis of the International Association for the Study of Lung Cancer (IASLC) database.

METHODS

Survival analyses were performed for clinically and pathologically staged patients presenting with SCLC from 1999 through 2010. Prognosis was compared in relation to the TNM seventh edition staging to serve as validation and analyzed in relation to proposed changes to the T descriptors found in the eighth edition.

RESULTS

There were 5002 patients: 4848 patients with clinical and 582 with pathological stages. Among these, 428 had both. Survival differences were confirmed for T and N categories and maintained in relation to proposed revisions to T descriptors for seventh edition TNM categories and proposed changes in the eighth edition. There were also survival differences, notably at 12 months, in patients with brain-only single-site metastasis (SSM) compared to SSM at other sites, and SSM without a pleural effusion showed a better prognosis than other patients in the M1b category.

CONCLUSION

We confirm the prognostic value of clinical and pathological TNM staging in patients with SCLC, and recommend continued usage for SCLC in relation to proposed changes to T, N, and M descriptors for NSCLC in the eighth edition. However, for M descriptors, it remains uncertain whether survival differences in patients with SSM in the brain simply reflect better treatment options rather than better survival based on anatomic extent of disease.

Whey protein gel composites in the diet of goats increased the omega-3 and omega-6 content of milk fat

Previously, feeding whey protein gels containing polyunsaturated fatty acids (PUFA) reduced their rumen biohydrogenation and increased their concentration in milk fat of Holstein cows. Our objective was to test the efficacy of whey protein isolate (WPI) gels produced in a steam tunnel as a method to alter the fatty acid (FA) composition of the milk lipids. Four primiparous Lamancha goats in midlactation were fed three diets in a 3 × 4 Latin square design. The WPI gels were added to a basal concentrate mix that contained one of three lipid sources: (i) 100% soya bean oil (S) to create (WPI/S), (ii) a 1:1 (wt/wt) mixture of S and linseed (L) oil to create (WPI/SL), or (iii) 100% L to create (WPI/L). Periods were 22 days with the first 10 days used as an adjustment phase followed by a 12-day experimental phase. During the adjustment phase, all goats received a rumen available source of lipid, yellow grease, to provide a baseline for milk FA composition. During the experimental phase, each goat received its assigned WPI. Milk FA concentration of C18:2 n-6 and C18:3 n-3 reached 9.3 and 1.64 g/100 g FA, respectively, when goats were fed WPI/S. Feeding WPI/SL increased the C18:2 n-6 and C18:3 n-3 concentration to 6.22 and 4.36 g/100 g FA, and WPI/L increased C18:2 n-6 and C18:3 n-3 to 3.96 and 6.13 g/100 g FA respectively. The adjusted transfer efficiency (%) of C18:3 n-3 to milk FA decreased significantly as dietary C18:3 n-3 intake increased. Adjusted transfer efficiency for C18:2 n-6 did not change with increasing intake of C18:2 n-6. The WPI gels were effective at reducing rumen biohydrogenation of PUFA; however, we observed a change in the proportion increase of C18:3 n-3 in milk FA suggesting possible regulation of n-3 FA to the lactating caprine mammary gland.

Treatment time, ease of use and cost associated with use of Equashield™, PhaSeal® , or no closed system transfer device for administration of cancer chemotherapy to a dog model

This prospective experimental simulation study evaluated the efficiency, ease of use (EOU) and cost of administering chemotherapy with two closed system transfer devices (CSTD, Equashield™ and PhaSeal^® ) and no CSTD. Forty-six veterinary technicians (VT) working in oncology specialty practices were timed during chemotherapy administration simulated with water and a model canine limb 10 times with each system and with no CSTD. EOU and likelihood of recommending each system were rated by VT using visual analog scales. Costs were obtained from veterinary distributors. Administration was fastest with Equashield™ (P = 0.0003), but the difference was not enough to affect case flow. Equashield™ was easier to use than PhaSeal^® or no CSTD (P = 0.002), however VT recommended both CSTD more strongly than no CSTD (P < 0.0001). Equashield™ cost less than PhaSeal^® but was sold only in bulk quantities. CSTD did not decrease efficiency in administering chemotherapy and were readily accepted by VT.

Observation of a reflected shock in an indirectly driven spherical implosion at the national ignition facility

A 200  μm radius hot spot at more than 2 keV temperature, 1  g/cm^{3} density has been achieved on the National Ignition Facility using a near vacuum hohlraum. The implosion exhibits ideal one-dimensional behavior and 99% laser-to-hohlraum coupling. The low opacity of the remaining shell at bang time allows for a measurement of the x-ray emission of the reflected central shock in a deuterium plasma. Comparison with 1D hydrodynamic simulations puts constraints on electron-ion collisions and heat conduction. Results are consistent with classical (Spitzer-Harm) heat flux.

Halitosis management by the general dental practitioner--results of an international consensus workshop

Clinical investigations on patients suffering from halitosis clearly reveal that in the vast majority of cases the source for an offensive breath odor can be found within the oral cavity (90%). Based on these studies, the main sources for intra-oral halitosis where tongue coating, gingivitis/periodontitis or a combination of the two. Thus, it is perfectly logical that general dental practitioners (GDPs) should be able to manage intra-oral halitosis under the conditions found in a normal dental practice. However, GDPs who are interested in diagnosing and treating halitosis are challenged to incorporate scientifically based strategies for use in their clinics. Therefore, the present paper summarizes the results of a consensus workshop of international authorities held with the aim to reach a consensus on general guidelines on how to assess and diagnose patients' breath odor concerns and general guidelines on regimens for the treatment of halitosis.

Does neighbourhood walkability moderate the effects of mass media communication strategies to promote regular physical activity?

BACKGROUND

Mass media campaigns are widely used in Australia and elsewhere to promote physical activity among adults. Neighbourhood walkability is consistently shown to be associated with walking and total activity. Campaigns may have different effects on individuals living in high and low walkable neighbourhoods.

PURPOSE

The purpose of this study is to compare pre- and post-campaign cognitive and behavioural impacts of the Heart Foundation's Find Thirty every day® campaign, in respondents living in high and lower walkable neighbourhoods.

METHODS

Pre- and post-campaign cross-sectional survey data were linked with objectively measured neighbourhood walkability. Cognitive and behavioural impacts were assessed using logistic regression stratified by walkability.

RESULTS

Cognitive impacts were significantly higher post-campaign and consistently higher in respondents in high compared with lower walkable neighbourhoods. Post campaign sufficient activity was significantly higher and transport walking significantly lower, but only in residents of lower walkable areas.

CONCLUSIONS

Cognitive impacts of mass media physical activity campaigns may be enhanced by living in a more walkable neighbourhood.

Would you Find Thirty online? Website use in a Western Australian physical activity campaign

ISSUE ADDRESSED

Mass media campaigns have used a range of traditional media (television, radio and print) to communicate health messages. In the past decade the Internet has added to these traditional methods with Web 2.0, smart phone technology and interactive media. 'Find Thirty every day(®)', a Western Australia population-wide mass media campaign delivered over 2 years, used a combination of traditional mass media, a website, online resources and banner advertising. The aim of the present study is to describe the use of the Find Thirty every day(®) website during the campaign media activities of May 2008-June 2010.

METHODS

Cross-sectional self-reported survey data were collected from a random sample of adults using a computer-assisted telephone interview over the period February-March 2010. Objective online analytical measures of unique visits to the Find Thirty every day(®) website were collected between June 2008 and June 2010.

RESULTS

Monthly visitors to the Find Thirty every day(®) website increased from 3193 in 2009 to 4374 in 2010. During the last two media waves (October 2009 and February 2010), site visits were 5388 and 5272 per month, respectively.

CONCLUSION

The impact of the Find Thirty every day(®) website was a positive outcome, considering the minimal online presence. SO WHAT? Health communication campaign planners should maximise the potential synergy of traditional mass media and new social media in future campaigns. Accordingly, a multidisciplinary approach that includes communication researchers, experts in information systems and a creative team experienced in online environments will need to be the way forward.

Tadalafil - a therapeutic option in the management of BPH-LUTS

BACKGROUND/AIMS

Men with signs of benign prostatic hyperplasia (BPH) may experience lower urinary tract symptoms (LUTS) such as urinary frequency, urgency, intermittence, nocturia, straining, incomplete emptying or a weak urinary stream. The effective management of LUTS suggestive of BPH (BPH-LUTS) requires careful consideration of several factors, including the severity of a patient's symptoms, concurrent or other coexisting medical conditions, the ability to improve symptoms and impact quality of life (QOL), as well as the potential side effects of available treatment options. Several clinical studies have assessed phosphodiesterase type 5 (PDE5) inhibitors in reducing LUTS; however, tadalafil is the only PDE5 inhibitor approved for the treatment of signs and symptoms of BPH, as well as in men with both erectile dysfunction (ED) and the signs and symptoms of BPH. This review examined articles that assessed tadalafil in patients with signs and symptoms of BPH, with or without erectile dysfunction (ED), which led to regulatory approval in the United States and Europe.

RESULTS

In dose-ranging and confirmatory studies, results demonstrate that tadalafil significantly improved total International Prostate Symptom Score (IPSS) following 12 weeks of treatment with once daily tadalafil 5 mg. Statistically significant improvements in Benign Prostatic Hyperplasia Impact Index (BII), IPSS subscores, IPSS QOL and International Index of Erectile Function (IIEF) were also observed. Improvement in urinary symptoms occurred regardless of age, previous treatment with an α1 -adrenergic blocker, BPH-LUTS severity at baseline or ED status.

CONCLUSIONS

While tadalafil is most frequently recognised as a standard treatment option for men with ED, it also represents a well-tolerated and effective treatment option in men with moderate to severe BPH-LUTS.

Effect of strong coupling on the dust acoustic instability

In a plasma containing charged dust grains, the dust acoustic instability (DAI) can be driven by ions streaming through the dust with speed less than the ion thermal speed. When the dust is strongly coupled in the liquid phase, the dispersion relation of the dust acoustic modes changes in a way that leads to an enhancement of the growth rate of the DAI. In this paper, we show how strong coupling enhances the DAI growth rate and consider application to microgravity experiments where subthermal ion flows are in general possible.

Interobserver agreement for the detection of Barrett's esophagus with optical frequency domain imaging

BACKGROUND

Optical frequency domain imaging (OFDI) is a second-generation form of optical coherence tomography (OCT) providing comprehensive cross-sectional views of the distal esophagus at a resolution of ~7 μm.

AIM

Using validated OCT criteria for squamous mucosa, gastric cardia mucosa, and Barrett's esophagus (BE), the objective of this study was to determine the inter- and intra-observer agreements by a large number of OFDI readers for differentiating these tissues.

METHODS

OFDI images were obtained from nine subjects undergoing screening and surveillance for BE. Sixty-four OFDI image regions of interest were randomly selected for review. A training set of 19 images was compiled distinguishing squamous mucosa from gastric cardia and BE using previously validated OCT criteria. The ten readers then interpreted images in a test set of 45 different images of squamous mucosa (n = 15), gastric cardia (n = 15), or BE (n = 15). Interobserver agreement differentiating the three tissue types and BE versus non-BE mucosa was determined using multi-rater Fleiss's κ value. The images were later randomized again and four readers repeated the test 3 weeks later to assess intraobserver reliability.

RESULTS

All ten readers showed excellent agreement for the differentiation of BE versus non-BE mucosa (κ = 0.811 p < 0.0001) and for differentiating BE versus gastric cardia versus squamous mucosa (κ = 0.866, p < 0.0001). For the four readers who repeated the test, the median intraobserver agreement (BE vs. non-BE) was high (κ = 0.975, IQR: 0.94, 1.0).

CONCLUSIONS

Trained readers have a high interobserver agreement for differentiating BE, squamous, and gastric cardia mucosa using OFDI.

The selective sphingosine 1-phosphate receptor modulator BAF312 redirects lymphocyte distribution and has species-specific effects on heart rate

BACKGROUND AND PURPOSE

BAF312 is a next-generation sphingosine 1-phosphate (S1P) receptor modulator, selective for S1P₁ and S1P₅ receptors. S1P₁ receptors are essential for lymphocyte egress from lymph nodes and a drug target in immune-mediated diseases. Here, we have characterized the immunomodulatory potential of BAF312 and the S1P receptor-mediated effects on heart rate using preclinical and human data.

EXPERIMENTAL APPROACH

BAF312 was tested in a rat experimental autoimmune encephalomyelitis (EAE) model. Electrophysiological recordings of G-protein-coupled inwardly rectifying potassium (GIRK) channels were carried out in human atrial myocytes. A Phase I multiple-dose trial studied the pharmacokinetics, pharmacodynamics and safety of BAF312 in 48 healthy subjects.

KEY RESULTS

BAF312 effectively suppressed EAE in rats by internalizing S1P₁ receptors, rendering them insensitive to the egress signal from lymph nodes. In healthy volunteers, BAF312 caused preferential decreases in CD4⁺ T cells, T_naïve, T_{central memory} and B cells within 4–6 h. Cell counts returned to normal ranges within a week after stopping treatment, in line with the elimination half-life of BAF312. Despite sparing S1P₃ receptors (associated with bradycardia in mice), BAF312 induced rapid, transient (day 1 only) bradycardia in humans. BAF312-mediated activation of GIRK channels in human atrial myocytes can fully explain the bradycardia.

CONCLUSION AND IMPLICATIONS

This study illustrates species-specific differences in S1P receptor specificity for first-dose cardiac effects. Based on its profound but rapidly reversible inhibition of lymphocyte trafficking, BAF312 may have potential as a treatment for immune-mediated diseases.

Advances in compact proton spectrometers for inertial-confinement fusion and plasma nuclear science

Compact wedge-range-filter proton spectrometers cover proton energies ∼3-20 MeV. They have been used at the OMEGA laser facility for more than a decade for measuring spectra of primary D(3)He protons in D(3)He implosions, secondary D(3)He protons in DD implosions, and ablator protons in DT implosions; they are now being used also at the National Ignition Facility. The spectra are used to determine proton yields, shell areal density at shock-bang time and compression-bang time, fuel areal density, and implosion symmetry. There have been changes in fabrication and in analysis algorithms, resulting in a wider energy range, better accuracy and precision, and better robustness for survivability with indirect-drive inertial-confinement-fusion experiments.

A randomized trial investigating the efficacy and safety of water soluble micellar paclitaxel (Paccal Vet) for treatment of nonresectable grade 2 or 3 mast cell tumors in dogs

BACKGROUND

Effective treatments for dogs with advanced stage mast cell tumors (MCT) remain a pressing need. A micellar formulation of paclitaxel (paclitaxel [micellar]) has shown promise in early-phase studies.

HYPOTHESIS/OBJECTIVES

The objective was to demonstrate greater activity for paclitaxel (micellar) compared with lomustine. The null hypothesis was μ(p) = μ(L) (ie, proportion of responders for the paclitaxel [micellar] and lomustine groups, respectively).

ANIMALS

Two hundred and fifty-two dogs with advanced stage nonresectable grade 2 or 3 MCT.

METHODS

Prospective multicenter randomized double-blind positive-controlled clinical trial. The primary endpoint was confirmed overall response rate (CORR) at 14 weeks. A secondary endpoint, biologic observed response rate (BORR), also was calculated. Safety was assessed by the characterization and grading of adverse events (AE).

RESULTS

Overall CORR (7% versus 1%; P = .048) and BORR (23% versus 10%; P = .012) were greater for paclitaxel (micellar) compared with lomustine. Paclitaxel (micellar)-treated dogs were 6.5 times more likely to have a confirmed response and 3.1 times more likely to experience a biologic observed response. The majority of AE with paclitaxel (micellar) were transient and clinically manageable. Twenty-seven dogs (33%) receiving lomustine were discontinued because of hepatopathy compared with 3 dogs (2%) receiving paclitaxel (micellar) (P < .0001; odds ratio 26.7).

CONCLUSIONS AND CLINICAL IMPORTANCE

Paclitaxel (micellar)'s activity and safety profile are superior to lomustine. The addition of an active and novel taxane to the veterinary armamentarium could fill a substantial need and, as its mechanism of action and AE profile do not overlap with currently available TKI, its availability could lead to effective combination protocols.

Upgrade of the MIT Linear Electrostatic Ion Accelerator (LEIA) for nuclear diagnostics development for Omega, Z and the NIF

The MIT Linear Electrostatic Ion Accelerator (LEIA) generates DD and D(3)He fusion products for the development of nuclear diagnostics for Omega, Z, and the National Ignition Facility (NIF). Significant improvements to the system in recent years are presented. Fusion reaction rates, as high as 10(7) s(-1) and 10(6) s(-1) for DD and D(3)He, respectively, are now well regulated with a new ion source and electronic gas control system. Charged fusion products are more accurately characterized, which allows for better calibration of existing nuclear diagnostics. In addition, in situ measurements of the on-target beam profile, made with a CCD camera, are used to determine the metrology of the fusion-product source for particle-counting applications. Finally, neutron diagnostics development has been facilitated by detailed Monte Carlo N-Particle Transport (MCNP) modeling of neutrons in the accelerator target chamber, which is used to correct for scattering within the system. These recent improvements have resulted in a versatile platform, which continues to support the existing nuclear diagnostics while simultaneously facilitating the development of new diagnostics in aid of the National Ignition Campaign at the National Ignition Facility.

[Cardiopulmonary emergencies during pregnancy and the postpartum period]

The number of patients who develop cardiac problems during pregnancy are increasing and represent to date the major cause of maternal death in western countries. Pregnancy induces several changes which together increase the hemodynamic burden on the cardiovascular system and can also cause a prothrombotic state. Hence, latent or apparent cardiac disease can acutely decompensate during pregnancy. From a cardiovascular perspective, pregnancies are most often complicated by acute coronary syndromes, peripartum cardiomyopathy, arrhythmias, or pulmonary embolism. Due to potential fetal harm conventional diagnostic and therapeutic approaches are limited by the restricted use of radiogenic cardiac imaging and applicable medications. Therefore, knowledge about available therapeutic options is of greatest importance, since guideline recommendations have clearly been demonstrated to reduce morbidity and mortality in acute cardiac emergencies during pregnancy.

Theoretical study on the possible use of SiC microparticles as photothermal agents for the heating of bacteria

Gold nanoparticles exhibiting surface plasmon resonances have been considered as photothermal agents for the selective destruction of bacteria by visible to near-infrared radiation. Here, we consider theoretically the possible complementary use of sub-micron silicon carbide (SiC) particles as photothermal agents for the heating of bacteria by pulsed mid-infrared (MIR) radiation. A SiC microparticle can exhibit surface phonon resonances in the MIR. Similar to the effect of surface plasmon resonances in gold nanoparticles, this could lead to enhanced absorption at the resonant wavelength and strong heating of the microparticle locally. If the heating is sufficient, this might lead to damage of bacterial cells adjacent to SiC particles. We estimate the heating of sub-micron SiC particles in a water medium under various pulse lengths of radiation at wavelength 10.6 μm. Noting that SiC is being investigated as a biocompatible material that could be functionalized for biomedical applications, and that an appropriately roughened SiC surface could be expected to exhibit similar surface phonon resonances, we speculate that enhanced heating under MIR radiation may be useful for in vitro sterilization of such surfaces.

A healthy bladder: a consensus statement

A panel of experts in urology, urogynecology, nursing, and behavioral therapy convened in 2010 to discuss the importance of a healthy bladder on overall health. They determined that a consensus statement was necessary to raise awareness among the general public, healthcare providers, payors, and policymakers, with the goals of minimizing the impact of poor bladder health and stimulating primary prevention of bladder conditions. In this statement, 'healthy' bladder function is described, as well as internal and external factors that influence bladder health. It is suggested that primary prevention strategies should be aimed at providing education regarding normal lower urinary tract structures and functioning to the public, including patients and healthcare providers. This education may promote the achievement of optimal bladder health by increasing healthy bladder habits and behaviors, awareness of risk factors, healthcare seeking, and clinician engagement and reducing stigma and other barriers to treatment. Promoting optimal bladder health may reduce the personal, societal and economic impact of bladder conditions, including anxiety and depression and costs associated with conditions or diseases and their treatment. While adopting healthy bladder habits and behaviors and behaviors may improve or maintain bladder health, it is important to recognize that certain symptoms may indicate the presence of conditions that require medical attention; many bladder conditions are treatable with a range of options for most bladder conditions. Lastly, the authors propose clinical directives based on persuasive and convergent research to improve and maintain bladder health. The authors hope that this statement will lead to promotion and achievement of optimal bladder health, which may improve overall health and help minimize the effects of bladder conditions on the public, healthcare professionals, educators, employers, and payors. The advisors are in consensus regarding the recommendations for improving and maintaining bladder health presented herein.

Role of Thin Fimbriae in Adherence and Growth of Acinetobacter calcoaceticus RAG-1 on Hexadecane

Acinetobacter calcoaceticus RAG-1, a hydrocarbon-degrading bacterium which adheres avidly to hydrocarbons and other hydrophobic surfaces, possesses numerous thin fimbriae (ca. 3.5-nm diameter) on the cell surface. MR-481, a nonadherent mutant of RAG-1 which is unable to grow on hexadecane under conditions of limited emulsification and low initial cell density, lacks these fimbriae. Prolonged incubation of MR-481 in hexadecane medium enriched for partial adherence revertants. The reappearance of thin fimbriae was observed in all such revertant strains. RAG-1 cells and partial revertant strains were agglutinated in the presence of antibody, whereas MR-481 cells were not. Another mutant, AB15, which was previously isolated on the basis of its nonagglutinability in the presence of antibody, also lacked thin fimbriae and was conditionally nonadherent. Furthermore, strain AB15 was unable to grow on hexadecane medium. Adherence of RAG-1 cells to hexadecane was considerably reduced after shearing treatment. The material removed from the cell surface by shearing of RAG-1 and the partial revertant strains yielded a single antigenic band in RAG-1 and partial revertant strains, as observed by crossed immunoelectrophoresis. This band was absent in both fimbriae-less mutants, MR-481 and AB15. The data demonstrate that the thin fimbriae of RAG-1 (i) are a major factor in adherence to polystyrene and hydrocarbon, (ii) may be crucial in enabling growth of cells on hexadecane, and (iii) constitute the major cell surface agglutinogen.