Clinical and Molecular Determinants of PSA Response to Bipolar Androgen Therapy in Prostate Cancer

BACKGROUND

Bipolar Androgen Therapy (BAT) is a novel therapy known to be effective in a subset of men with metastatic castrate resistant prostate cancer (mCRPC). A better understanding of responders and non-responders to BAT would be useful to clinicians considering BAT therapy for patients. Herein we analyze clinical and genetic factors in responders/non-responders to better refine our understanding regarding which patients benefit from this innovative therapy.

METHODS

mCRPC patients were assessed for response or no response to BAT. Patients with PSA declines of greater than 50% from baseline after 2 or more doses of testosterone were considered to be responders. Whereas, Non-responders had no PSA decline after 2 doses of testosterone and subsequently manifest a PSA increase of >50%. Differences between these two groups of patients were analyzed using clinical and laboratory parameters. All patients underwent genomic testing using circulating tumor DNA (ctDNA) and germline testing pre-BAT.

RESULTS

Twenty five patients were non-responders and 16 were responders. Baseline characteristics between non-responders and responders varied. Responders were more likely to have had a radical prostatectomy as definitive therapy and were more likely to have been treated with an androgen receptor (AR) antagonist (enzalutamide or apalutamide) immediately prior to BAT (compared to abiraterone). Duration of prior enzalutamide therapy was longer in responders. Non-responders were more likely to have bone-only metastases and responders were more likely to have nodal metastases. Assays detected ctDNA AR amplifications more often in responding patients. Responders trended toward having the presence of more TP53 mutations at baseline.

CONCLUSIONS

BAT responders are distinct from non-responders in several ways however each of these distinctions are imperfect. Patterns of metastatic disease, prior therapies, duration of prior therapies, and genomics each contribute to an understanding of patients that will or will not respond. Additional studies are needed to refine the parameters that clinicians can utilize prior to choosing among the numerous treatment alternatives available for CRPC patients. This article is protected by copyright. All rights reserved.

Comparative ctDNA analyses of African-American and Caucasian patients with CRPC

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Background: Somatic genetic analyses have indicated genetic distinctions in AA as compared to C patients. In the Mahal et al. study (1) evaluating a broad spectrum of pts with tissue based assays, FOXA1 mutations were more frequent in AA men and TP53 mutations were less frequent in AA men as compared to C men. In a separate analysis by Khashab et al. (2) conducted in prostate cancer pts receiving androgen deprivation therapy, using both tissue and ctDNA assays, the authors reported AR, TP53, SPOP, and BRCA2 were more frequently mutated in AA men as compared to C men. Herein we assessed the Guardant 360 platform in assessing ctDNA differences in AA and C men, all of whom had CRPC at the time assays were performed. Methods: Guardant 360 was used to analyze ctDNA with a cut-off of >0.5% for allelic fractions for ascertaining the presence or absence of pathogenic mutations and various amplifications. Lower allelic fractions were not analyzed given these may represent less relevant mutations. Depending on the timing of the assays (2015-2021), 70-83 genes were analyzed. All pts had CRPC and all patients were treated at Tulane Cancer Center. Chi Square analyses were used to determine statistical differences. AR, BRCA2, and TP53 were assessed but SPOP and FOXA1 were not assessable in the Guardant ctDNA assay. Both mutations and amplifications were evaluated. Results: Among men with CRPC, a total of 48 AA men and 179 C men were analyzed using ctDNA. Clear distinctions were found in the alteration reported in APC, TP53, and CDK12. TP53 was less frequently mutated and other genes were more frequently altered in the AA men. Conclusions: Using Guardant ctDNA assays in men with CRPC, clear distinctions were found in AA men as compared to C men. It is unclear why these results differ from that reported by others, however distinctions in both the assays and the populations are notable.[Table: see text]

Longitudinal ctDNA alterations in germline positive CRPC patients

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Background: Circulating tumor-derived DNA (ctDNA) is an accessible method for characterizing somatic alterations. We report longitudinal ctDNA screenings of mCRPC patients (pts) who have had germline testing. Methods: Patients with both germline testing and ctDNA assessment were included. Germline testing was performed with a multi-gene cancer panel from Invitae (50-83 genes) and somatic alterations in ctDNA were identified by testing with Guardant 360 (70-83 genes). ctDNA alterations were characterized as deletions, frameshift, missense, nonsense, and other mutations. A total of 177 patients in various stages of therapy had both ctDNA and germline DNA tested. Results: From 2015-2021, 177 mCRPC patients were included and had an average of 3 ctDNA tests. 11.3% (20/177) had pathogenic or likely-pathogenic germline mutations. The common pathogenic germline mutations were in BRCA2 (25%; 5/20), ATM (10%; 2/20), and MSH2 (10%; 2/20). In ctDNA, missense mutations were the most prevalent type of gene alteration in germline negative (n = 539/790, 68%) and germline positive (n = 124/218, 57%) followed by frameshift mutations at 22% (n = 48/218) in germline positive and 10% (n = 80/790) in germline negative patients. Germline positive patients were more likely to have somatic frameshift mutations (OR = 2.09, 95% C.I. (1.3792, 3.1618), p = 0.001) and less likely to have missense mutations (OR = 0.61, 95% C.I. (0.4519, 0.8351), p = 0.002). Other alterations including deletions, nonsense, and other mutations were not significantly different. Of the germline positive pts, BRCA2 mutation was associated with the highest number of somatic alterations. Conclusions: Germline positive CRPC patients were more likely to have frameshift mutations and less likely to missense mutations compared to germline negative CRPC patients. Patients with germline mutations in BRCA2 and TP53 had the highest number of somatic alterations detected in ctDNA over the course of ctDNA evaluation.

Evaluation of ctDNA alterations in mCRPC patients with germline pathogenic mutations

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Background: Germline alterations are found in approximately 12-17% of CRPC patients. Similarly, evaluating tumoral changes with circulating tumor DNA (ctDNA) has become an increasingly useful tool for understanding mechanisms underpinning disease progression. In this study, we evaluated both germline and somatic genetic changes in patients with mCRPC. Methods: Patients included had germline screening and ctDNA analyzed with the Guardant 360 assay. All patients were CRPC at the time of Guardant testing. Germline alterations were classified as pathogenic/likely-pathogenic or not pathogenic. Only ctDNA alterations with an alleleic fraction greater than 0.5% were included in analyses. Additional evaluation of CRPC status, treatment history, family history and other clinical covariates are ongoing. Chi-square and Fischer’s Exact tests were used for comparison of cohorts. Results: A total of 168 Caucasian CRPC patients had Guardant 360 testing at time of progression and germline testing between 2015-2021. 61% (n = 102/168) of patients have previously had treatment with abiraterone, 49% (n = 82/168) have had Enzalutamide and 40% (n = 68/168) have had treatment with taxanes. 12% (n = 20/168) of CRPC patients had a pathogenic/likely-pathogenic (P/LPv) germline alteration, 46% (n = 77/168) had a germline variant of unknown significance (VUS), 42% (n = 71/168) were germline negative. CRPC patients with pathogenic germline mutations were significantly more likely to have subsequent somatic alterations in BRCA2 (OR = 5.05, 95% C.I. (1.11, 23.01), p = 0.055), NF1 (OR = 7.89, 95% C.I. (2.15, 28.10), p = 0.004), and TP53 (OR = 3.52, 95% C.I. (1.28, 9.68), p = 0.015). In TP53, among germline positive patients, 45% (n = 9/20) had TP53 alterations compared to 30% (n = 45/148) of germline negative patients. Conclusions: Germline positive (P/LPv) CRPC patients were significantly more likely to have somatic alterations in BRCA2, NF1, and TP53. Understanding the totality of genetic changes, both germline and acquired somatic alterations is essential as the arsenal of targeted treatment for CRPC continues to expand. Additional studies including longitudinal assessment genetic changes and clinical correlates will be necessary to evaluate these findings in the context of treatment outcomes and disease progression.

Circulating tumor DNA responses to high-dose testosterone injections in CRPC patients

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Background: Some proportion of men with CRPC have favorable responses to high doses of testosterone (HDT) and some do not. Genomic determinants of these responders and non-responders are poorly understood. Herein ctDNA predictors of response are assessed using a responder/non-responder analysis. Methods: All men with CRPC had been pretreated with abiraterone, enzalutamide, or both. A ctDNA test was obtained prior to high doses of testosterone (administered as a dose of 400 mg IM testosterone cypionate every 3-4 weeks). Guardant 360 was used to analyze ctDNA (with an allelic fraction cut-off of > 0.5%) to ascertain the presence or absence of pathogenic mutations. Lower allelic fractions were not analyzed. Responders had a PSA decline of 50% or more (N = 16), non-responders received at least two doses of testosterone but never had any PSA decline at all (N = 20). All patients were treated at Tulane Cancer Center. Results: AR amplifications were more commonly detected (p = 0.036) pre-treatment in the ctDNA of responders (5/16) as compared to non-responders (1/20). No differences were found in those with common AR mutations; T878A was detected in 2/16 responders and 2/20 non-responders, L702H was detected in 1/16 responders and 2/20 non-responders. No differences were seen with regard to TP53 mutations, 6/20 non-responders and 7/16 responders. Non- AR/non- TP53 mutations were not distinct in the two groups but trended (P = 0.15) toward being more common in non-responders (5/16 in responders versus 11/20 non-responders). Pre- and post- ctDNA analyses were conducted in 5/6 patients for those with AR amplification at baseline. In all 5 of these patients, the degree of AR amplification diminished after testosterone injections. Conclusions: In this analysis of CRPC patients who were responders and non-responders to 400 mg testosterone cypionate q 3-4 weeks (post-abiraterone and/or enzalutamide), only AR amplifications in ctDNA were predictive of response. In all measured patients, the degree of AR amplification in the ctDNA diminished after testosterone injections.

Ablation of atypical atrial flutters using ultra high density-activation sequence mapping

PURPOSE

The purpose of this study was to evaluate ultra high density-activation sequence mapping (UHD-ASM) for ablating atypical atrial flutters.

METHODS

For 23 patients with 31 atypical atrial flutters (AAF), we created UHD-ASM.

RESULTS

Demographics age = 65.3 ± 8.5 years, male = 78%, left atrial size = 4.66 ± 0.64 cm, redo ablation 20/23(87%). AAF were left atrial in 30 (97%). For each AAF, 1273 ± 697 points were used for UHD-ASM. Time to create and interpret the UHD-ASM was 20 ± 11 min. For every AAF, the entire circuit was identified. Thirty (97%) were macroreentry. AAF cycle length was 267 ± 49 ms, and the circuit length was 138 ± 38 mm (range 35-187). Macroreentry atrial flutters took varied pathways, but each had an area of slow conduction (ASC) averaging 16 ± 6 mm (range 6-29) in length. Entrainment was not utilized. We targeted the ASC and ablation terminated AAF directly in 19/31 (61.3%) and altered AAF activation in 7/31 (22.6%), all of which terminated directly with additional mapping/ablation. AAF degenerated to atrial fibrillation in 2/31 (6.5%) with RF and could not be reinduced after ASC ablation. Median time from initial ablation to AAF termination was 64 s. Thus, 28/31 (90.3%) terminated with RF energy and/or could not be reinduced after ASC ablation. At 1 year of follow-up, 77% were free of atrial tachycardia or atrial flutter and 61% were free of all atrial arrhythmias.

CONCLUSIONS

Using rapidly acquired UHD-ASM, the entire AAF circuit as well as the target ASC could be identified. Most AAF were left atrial macroreentry. Ablation of the ASC or microreentry focuses directly terminated or eliminated AAF in 90.3% without the need for entrainment mapping.

Abstract 3180: Regulation of stem cells by the tumor suppressor PP2A-B56α

Protein phosphatase 2 A (PP2A) is one of the major cellular Serine-Threonine phosphatases and regulates numerous signaling pathways, including stem cell self-renewal, proliferation, differentiation, and cell survival. The PP2A holoenzyme has 3 subunits: a catalytic (C) subunit, a structural (A) subunit, and a variable regulatory (B) subunit, which directs PP2A to specific targets. PP2A inhibition is required to completely transform human cells and siRNA screens have shown that loss of B56α, B56γ, or PR72/PR130 B subunits results in cell transformation, which are involved in negatively regulating oncogenic pathways including Wnt, Akt, and Myc. Moreover, PP2A plays an important role in regulating human embryonic stem cells, where both the A and C subunit levels and PP2A activity gradually increase during the course of differentiation. Our preliminary data also demonstrates in breast cancer cell lines that B56α overexpression decreases the number of mammospheres whereas inhibiting B56α increases them. Further research is needed to address the function of specific PP2A complexes in regulating stem cells. Despite the fact that B56α depletion is important for human cell transformation, no one has reported on its role in vivo and no mouse model has ever been generated to our knowledge. Therefore, to study the role of B56α in stem cells and cell transformation in vivo, we have generated B56α knockout mice.

We generated B56α knockout mice using commercially available gene trap ES cells. The gene trap sits in the first intron of the B56α gene and, through a splice acceptor site, splices out the first exon to the gene trap and therefore stops whole gene transcription in the whole body. The primary phenotypic effect we observed with B56α loss was spontaneous skin lesion formation. Thus far 40% of mice have developed skin lesions between 11 to 21 months and showed hyper-proliferation of the epidermis, hair follicles, and dermis. Increased number of hair follicles prompted us to perform stem cell assays using BrDU to label long term label-retaining cells and the colony assays for the fast adhering keratinocyte stem cells. We found an increase in skin stem cell numbers. In addition to skin lesions, we found increased inflammation both in skin lesions, liver, and spleen and some enlarged lymph nodes. Next we asked whether loss of B56α also increased the number of hematopoietic stem cell. Although the number of hematopoietic stem cells in the periphery was unchanged under normal condition, treating mice with granulocyte colony-stimulating factor increased the number of circulating stem cells.

Our model suggests that loss of B56α increases the number of stem cells and that B56α is important for cells to maintain homeostasis; B56α loss can lead to increased activity of important oncogenes, such as cMyc, leading to aberrant cell growth and defects in stem cell maintenance. More experiments need to be done to understand the primary effect of B56α loss in skin and the interplay between skin lesions and inflammation.

Citation Format: Mahnaz Janghorban, Derek Zachman, Xiaoyan Wang, Anupriya Agarwal, William Fleming, Rosalie Sears. Regulation of stem cells by the tumor suppressor PP2A-B56α. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3180. doi:10.1158/1538-7445.AM2015-3180

Environmental monitoring: setting alert and action limits based on a zero-inflated model

The primary purpose of an environmental monitoring program is to provide oversight for microbiological cleanliness of manufacturing operation and document the state of control of the facility. Key to the success of the program is the establishment of alert and action limits. In practice, several statistical methods including normal, Poisson, and negative binomial modeling have been routinely used to set these limits. However, data collected from clean rooms or controlled locations often display excess of zeros and overdispersion, caused by sampling population heterogeneity. Such data render it inappropriate to use the traditional methods to set alert and action levels. In this paper, a method based on a zero-inflated negative binomial model is proposed for the above instances. The method provides an enhanced alternative for trending environmental data of classified rooms, and it is demonstrated to show a clear improvement in terms of model fitting and parameter estimation.

LAY ABSTRACT

The primary purpose of an environmental monitoring program is to provide oversight for microbiological cleanliness of manufacturing operation and document the state of control of the facility. Key to the success of the program is the establishment of alert and action limits. In practice, several statistical methods including normal, Poisson, and negative binomial modeling have been routinely used to set these limits. However, data collected from clean rooms or controlled locations often display excess of zeros and overdispersion, caused by sampling population heterogeneity. Such data render it inappropriate to use the traditional methods to set alert and action levels. In this paper, a method based on a zero-inflated negative binomial model is proposed for the above instances. The method provides an enhanced alternative for trending environmental data of classified rooms, and it is demonstrated to show a clear improvement in terms of model fitting and parameter estimation.

Cervical pneumatocoele following total thyroidectomy

Cervical pneumatocoele following thyroidectomy is rare. Urgent surgical intervention is necessary in the setting of widespread tissue emphysema and respiratory embarrassment. We describe a patient with a large pneumatocoele presenting six weeks after a total thyroidectomy who was managed successfully without surgical re-exploration. We also discuss the aetiology of cervical pneumatocoele as well as the potential indications for operative versus conservative management.

Evaluation of the MicroWorks, Inc. Swab Sampling System (MSSSTM) for Use in Performing Quantitative Swab Sampling

The purpose of this study was to qualify the MicroWorks, Inc. Swab Sampling System (MSSS™) swab kit for use in sampling cleanroom surfaces for bioburden. A six-part study was performed to demonstrate the suitability of the swab materials, the recovery of bioburden from typical cleanroom surfaces, the neutralization of typical disinfectants used in cleanrooms, the removal of diluents from the swabbed surface, and the hold time for test samples. A total of 13 challenge organisms were used: six National Collection of Type Cultures/American Type Culture Collection (NCTC/ATCC) standard culture organisms and seven environmental isolates, which were recovered from different MedImmune manufacturing facilities. Based on the results of the study it was shown that 12 of the challenge organisms were recovered from the calcium alginate swab materials and 13 of the challenge organisms were recovered from the sodium citrate diluent at ≥70%. Eleven organisms, including the six NCTC/ATCC organisms and five of the environmental organisms, were recovered from stainless steel, glass, polyvinylchloride curtain material, latex glove material, and neoprene at a rate of ≥70%. Effective neutralization was shown for LpH (an acid phenolic compound manufactured by Steris Corporation, Mentor, OH), Vesphene II, Spor-Klenz, 70% isopropyl alcohol (IPA), and Biocides B, X, and Y when utilizing the filtration/rinsing process. Recovery of six NCTC/ATCC organisms was demonstrated at ≥70%. The study also demonstrated that the diluents could easily be removed from the swabbed surface by following the swab with a 70% IPA wipe. A hold time of at least 24 h was demonstrated when samples were stored at 2-8 °C. The results of this study demonstrated that the MSSS™ swab kit and qualified test method recover ≥70% of surface bioburden from common cleanroom surfaces in the presence of a wide variety of disinfectants.

Ectopic Parathyroid Adenoma With Tc-99m MIBI Washout

The authors present a case of a 71-year-old woman with clinical and biochemical features of primary hyperparathyroidism and a history of right pneumonectomy. An ultrasound scan did not demonstrate any abnormality. A planar Tc-99m methoxyisobutylisonitrile (Tc-99m MIBI) scan showed an area of minimally increased uptake within the right hemithorax. However, unlike most adenomas, this demonstrated washout similar to the thyroid at 90 minutes and 3 hours. Subsequent SPECT imaging clearly showed the lesion in the superior right hemithorax. A CT scan and angiogram confirmed the presence of this mass. After surgery, histology confirmed the diagnosis of a parathyroid adenoma. Postoperatively, the calcium and PTH levels returned to normal.

Renal cortical Na+-K+-ATPase activity and abundance is decreased in normal pregnant rats

During late pregnancy, the rat undergoes massive plasma volume expansion due to cumulative renal sodium retention. In the present study, conducted in virgin, mid- (days 11-13), and late-pregnant (days 18-20) rats, we measured both Na+-K+-ATPase activity (by coupled enzyme assay) and abundance of the alpha-subunits of the Na+-K+-ATPase (by Western and slot blot analyses) in renal cortex, medulla, and brain stem. Unexpectedly, Na+-K+-ATPase in renal cortex, in both stages of pregnancy, is reduced versus the virgin, consistent with our finding of a reduced quantity of the alpha1-subunit. In renal medulla, there is a small rise in activity at midterm, but there is no difference in either activity or abundance of the alpha1-subunit in late pregnancy, when renal Na retention is maximal. In brain stem, where only alpha2- and alpha3-subunits are evident, pregnancy has no impact on enzyme activity or abundance of either isoform. In conclusion, the outcome of these experiments was unexpected in that we did not observe increased renal Na+-K+-ATPase activity in late pregnancy in the rat. In fact, in renal cortex, Na+-K+-ATPase activity and abundance are reduced. Whatever promotes net sodium retention in pregnancy must be capable of overwhelming this and several other strong natriuretic signals.

Applications of virtual reality technology in pathology

TelePath(SM) a telerobotic system utilizing virtual microscope concepts based on high quality still digital imaging and aimed at real-time support for surgery by remote diagnosis of frozen sections. Many hospitals and clinics have an application for the remote practice of pathology, particularly in the area of reading frozen sections in support of surgery, commonly called anatomic pathology. The goal is to project the expertise of the pathologist into the remote setting by giving the pathologist access to the microscope slides with an image quality and human interface comparable to what the pathologist would experience at a real rather than a virtual microscope. A working prototype of a virtual microscope has been defined and constructed which has the needed performance in both the image quality and human interface areas for a pathologist to work remotely. This is accomplished through the use of telerobotics and an image quality which provides the virtual microscope the same diagnostic capabilities as a real microscope. The examination of frozen sections is performed a two-dimensional world. The remote pathologist is in a virtual world with the same capabilities as a "real" microscope, but response times may be slower depending on the specific computing and telecommunication environments. The TelePath system has capabilities far beyond a normal biological microscope, such as the ability to create a low power image of the entire sample using multiple images digitally matched together; the ability to digitally retrace a viewing trajectory; and the ability to archive images using CD ROM and other mass storage devices.

Load bearing and deformation characteristics of monofilament nylon 66 and their implications for ophthalmic surgery

The load bearing and deformation characteristics of monofilament nylon 66 have been examined. This material has been shown to have increased strength and altered deformation properties compared to bulk nylon. These features are beneficial in its role as a corneal suture. However, the load bearing performance of monofilament nylon 66 has been shown to be influenced by the manner in which it is stressed, making the task of producing identical stitches difficult. Moreover, a period of rapid relaxation has been shown to occur immediately after installation which makes the time taken to install the suture a critical factor in its subsequent performance. These factors, which are essentially beyond the control of the ophthalmic surgeon, must surely play a significant role in the inconsistent post operative results seen.

The use of transjugular intrahepatic portosystemic shunt and surgical portocaval H-shunt for the treatment of colorectal variceal bleeding

Surgical portocaval H-shunt was performed after the thrombosis of a transjugular intrahepatic portosystemic shunt inserted for colorectal variceal bleeding. The surgical procedure successfully controlled the variceal bleeding. However, the patient developed postoperative liver failure and hepatic encephalopathy due to complete portal vein thrombosis and the absence of prograde portal flow. This case illustrates the potential risks of the serial use of transjugular intrahepatic portosystemic shunt and surgical portocaval shunt leading to complete portal vein thrombosis, hepatic encephalopathy and acute liver failure.

Some mechanical properties of 10/0 monofilament nylon sutures

A short pilot study is described which investigates some of the mechanical properties of ophthalmic sutures. The Alcon 10/0 monofilament nylon suture was found to behave in a mechanically consistent manner. Like all nylon it possesses the property of 'creep', which helps to compensate for overtightening of the section during surgery.

A new steroid-eluting epicardial lead: experience with atrial and ventricular implantation in the immature swine

The first study with investigational steroid epicardial leads was carried out in mature canine with prototype leads. Because the demand for epicardial leads is highest in small infants and the prototype steroid-eluting lead has been redesigned, this study was carried out in immature swine to evaluate the newly designed lead. Six immature swine (2 at 5 weeks of age and 4 at 6 weeks) underwent epicardial implantation of four porous platinized tip leads: one steroid and one nonsteroid on the right atrium; one steroid and one nonsteroid on the right ventricle. At implantation, the lead terminals were connected to a percutaneous access device subcutaneously placed in the right lateral neck. This allowed chronic measurements by using an insulated needle connected with a cable to the pacing systems analyzer. Measurements were obtained at implantation and weekly for 3 weeks. Compared to the nonsteroid atrial leads, the steroid atrial leads had lower mean thresholds (P less than 0.01) at 1, 2, and 3 weeks after implantation. The mean threshold values from ventricular steroid leads were also lower and exhibited little increase from implant with the highest mean threshold of only 1.02 V, however, a statistically significant difference between steroid and nonsteroid was not reached. This newly designed steroid epicardial lead provided favorable results for continual human clinical study.

Comparison of two myoepicardial pacemaker leads: follow-up in 80 children, adolescents, and young adults

Although several types of commercially available epicardial leads exist, few postimplantation data have been reported. To compare "screw-in" (6917-35) leads with "stab-on" leads (4951-35) from the same manufacturer, we reviewed the records of 80 young patients (age 8 days to 29 years) who underwent ventricular epicardial pacemaker implantation from 1973 to 1986. Follow-up for the 57 patients with the 6917-35 model ranged from 3 months to 17 years (median 6.5 years) and for the 23 patients with the 4951-35 model 9 days to 4.25 years (median 2.0 years). Actuarial life table analysis revealed significantly (P less than 0.001) fewer 4951-35 leads were functioning at each of 1-5 years after implant, compared to the 6917-35 leads. Analysis of available threshold pulse width data revealed no difference (P = 0.08) acutely (6 weeks after implant), but a significantly (P = 0.05) higher mean threshold for the 4951-35 leads was found chronically. No significant correlation was found for lead failure with age, underlying heart disease, lead site (i.e., left or right ventricle), or surgical approach. Using the sutureless, stab-on technique, the 4951-35 lead is associated with higher thresholds and lower survival rate when compared to the 6917-35 lead.

Distinctive biochemical features of Salmonella dublin isolated in California

We examined 34 strains of Salmonella dublin that were isolated in California between 1978 and 1982. All were of a characteristic biotype; they did not grow on Simmons citrate or acetate and did not ferment arabinose. Their apparent inability to use citrate as the only carbon source was due to a nutritional requirement for nicotinic acid. Because S. dublin strains are of a characteristic biotype, are host adapted to bovines, and are unusually virulent for humans, we suggest that S. dublin be considered a separate species of the genus Salmonella. It is important that clinical laboratories recognize and differentiate this organism from less pathogenic salmonellae so that they can alert clinicians to the presence of this invasive microorganism.

Nitrate reduction: new method for testing the antibiotic susceptibility of Haemophilus influenzae

We have developed a new micro-broth-dilution assay for determining the antimicrobial susceptibility of Haemophilus influenzae. This assay is based on the ability of viable H. influenzae to reduce nitrates to nitrites. Bacterial viability is detected by a positive nitrite reaction rather than visible turbidity. The nitrate reduction assay was compared with a standard microassay using 51 isolates of H. influenzae and six beta-lactam antibiotics. Although there was good agreement between the two methods, the nitrate reduction assay was more sensitive in detecting viable bacteria, and so established a more accurate estimate of the minimal inhibitory concentration. The nitrate reduction assay offered the additional advantage that it could be used to determine the minimal bactericidal concentration without having to subculture the broth. Ampicillin, penicillin, and cefamandole were equally effective in vitro against susceptible strains (minimal inhibitory concentrations, 0.125 to 0.5 mug/ml), whereas all three antibiotics were ineffective against two beta-lactamase-producing strains. Using the nitrate reduction assay, resistance to cefamandole was detectable with inoculum sizes ranging from 10(4) to 10(6) colony-forming units per ml, while the turbidity assay detected resistance only with the largest inoculum.

The Isotopic Constitution of Igneous Sulphur and the Primordial Abundance of the Terrestrial Sulphur Isotopes

not available