Changes in body composition in early breast cancer patients treated with aromatase inhibitors.

PURPOSE: The aim of the study was to analyze the modification of total and regional body composition in early breast cancer patients treated with aromatase inhibitors (AIs). METHODS: This is a prospective, single-center, observational, longitudinal study. Four-hundred and twenty-eight patients treated with adjuvant aromatase inhibitors were enrolled at the Medical Oncology and Breast Unit of Spedali Civili Hospital in Brescia from September 2014 to June 2022. Several body composition parameters including total and regional fat and lean body mass were investigated with dual-energy X-ray absorptiometry (DXA) scan at baseline and after 18 months of treatment with aromatase inhibitors. RESULTS: A significant increase in fat body mass (mean + 7.2%, 95% confidence interval [CI]: 5.5;8.9%) and a reduction in lean body mass (mean -3.1%, 95% CI -3.9; -2.4) were documented in this population. The changes in fat and lean body mass varied considerably according to different body districts ranging between + 3.2% to + 10.9% and from-1.3% to -3.9%, respectively. CONCLUSION: Aromatase inhibitor adjuvant therapy in early breast cancer is associated with changes in body composition, with a wide variability among different body districts, leading to a risk of sarcopenic obesity. Supervised physical exercise that focuses on single body parts that may display detrimental variations may be beneficial for AIs treated patients.

The combination of insulin resistance and visceral adipose tissue estimation improves the performance of metabolic syndrome as a predictor of type 2 diabetes.

AIMS: To assess the performance of metabolic syndrome as a predictor of type 2 diabetes in a model that also includes both a measure of insulin resistance and a metabolic score for visceral fat, and to propose a novel metabolic syndrome definition. METHODS: In a prospective Metabolic Syndrome Cohort (n=6143), we evaluated improvements in type 2 diabetes risk prediction using International Diabetes Federation-defined and Adult Treatment Panel III-defined metabolic syndrome, after inclusion in the model of updated homeostatic model assessment of insulin resistance and a metabolic score for visceral fat. We also developed a modified metabolic syndrome construct, 'MS-METS', which used the metabolic score for visceral fat instead of waist circumference to evaluate improved predictive performance for risk of developing type 2 diabetes. RESULTS: Participants who had metabolic syndrome as defined by both the Adult Treatment Panel III and the International Diabetes Federation criteria had a higher risk of type 2 diabetes compared to participants who did not meet these criteria. Addition of updated homeostatic model assessment of insulin resistance and metabolic score for visceral fat to both metabolic syndrome definitions increased predictive performance for type 2 diabetes risk. Homeostatic model assessment of insulin resistance was the only additional predictor of type 2 diabetes in participants without metabolic syndrome. Conversely, in participants with metabolic syndrome, the use of the metabolic score for visceral fat was the stronger added predictor for type 2 diabetes. When evaluating participants using the MS-METS definition we observed the largest improvement in predictive ability for type 2 diabetes risk and a significant reduction in risk overestimation compared to evaluation using metabolic syndrome defined according to the International Diabetes Federation and Adult Treatment Panel III criteria alone. CONCLUSION: Inclusion of updated homeostatic model assessment of insulin resistance and metabolic score for visceral fat increases performance of metabolic syndrome in prediction of type 2 diabetes. Assessment of insulin resistance could be more useful than conventional metabolic syndrome and assessment of visceral adipose tissue could be more useful in people with metabolic syndrome. Metabolic syndrome as defined using our modified MS-METS construct improved the accuracy of type 2 diabetes prediction.

Semi-quantitative pulmonary congestion score: prevalence and diuretic management implications after heart failure discharge.

INTRODUCTION: Persistent congestion after heart failure (HF) discharge is associated with a higher risk of readmissions. MATERIAL AND METHODS: eighty-two patients included after HF discharge. The aim of the study was to characterize semiquantitatively the degree of pulmonary congestion and its changes, describing the relationship between these findings and diuretic management. RESULTS: On the first visit, despite the absence of clinical congestion in the majority of patients, half of the had some degree of pulmonary congestion by ultrasound. After global assessment in this initial visit (clinical and ultrasound) the diuretic was lowered in 50 patients (60%), kept the same in 16 (20%) and it was increased in the rest. In the 45 patients without ultrasound congestion, diuretic reduction was attempted in 80%, being this strategy successful in the majority of them. CONCLUSIONS: Lung ultrasound, using simple quantification methods, allows its real incorporation into clinical practice, helping us in the decision making process.

Esophageal eosinophilia after radiofrequency ablation for Barrett's esophagus.

Radiofrequency ablation (RFA) with HALO system has been developed as a new treatment option for Barrett's esophagus (BE). It had been observed that some patients had esophageal eosinophilia (EE) infiltration after RFA. The incidence and features of EE after RFA were systematically determined. From a prospectively compiled database, data on 148 patients who underwent RFA for BE were analyzed. Biopsies were taken pre- and post-RFA from the BE segment, and histological sections of the biopsy specimens were stained with hematoxylin and eosin, and examined by a gastrointestinal pathologist. The incidence of EE post-RFA was then determined. Of the 148 patients, 120 (81%) were men, 137 (92%) were white, 64 (43%) were overweight and 49 (33%) obese, and 128 (86%) were over 50 years of age or more. Four (2.7%) of the patients developed post-RFA EE, but none had symptoms of eosinophilic esophagitis. All patients except one had a history of seasonal allergies. All four were taking proton pump inhibitor before and after RFA. Two patients with EE drank alcohol, one of which was a smoker. EE is a potential adverse event of RFA for BE. The absence of esophageal dysfunction symptoms suggests a different clinicopathological entity from eosinophilic esophagitis. Further studies should be done to assess its clinical significance, if therapy is needed, or if it may eventually lead to eosinophilic esophagitis.

First detection of porcine circovirus type 2e in Europe.

Porcine circovirus 2 (PCV-2) infections are among the most economically important in swine farming. Because of the high evolutionary rate of PCV-2, several variants have emerged and are currently classified into several genotypes. However, only three (i.e. PCV-2a, PCV-2b, and PCV-2d) have a worldwide distribution, with other genotypes restricted to certain geographical regions and/or for limited time periods. Underdiagnosis or underreporting of these genotypes cannot be excluded. This is the first report of the detection and genetic characterisation of the PCV-2e genotype in Europe, from sows on a farm in Italy showing no clinical evidence of porcine circovirus disease. A follow-up study demonstrated persistent subclinical evidence of PCV-2e on the farm, at low frequency and viral load. This incidental finding emphasises the need for more intensive routine monitoring activities involving asymptomatic animals, coupled with DNA sequencing and data sharing. Considering the relevant genetic and phenotypic divergence of such genotypes, the actual efficacy of currently applied vaccines and diagnostic assays should be further evaluated.

Simulation of the Physiological Characteristics of Pillar and Modiolar Fibers of the Auditory Nerve.

The study of the physiological characteristics of the auditory nerve fibers is fundamental to understand their capability to encode sounds. These characteristics include their spontaneous firing rate, their threshold, and their dynamic range. Although it is possible to perform in vitro recordings of these characteristics in different cell models, it is complicated to obtain in vivo measurements of them directly from the cochlea. For example, the apex of the cochlea since it is an unreachable region which is vulnerable to surgical trauma that could result in altered recordings. In this paper, the behavior of Pillar and Modiolar fibers of the auditory nerve were simulated in response to tone bursts of different frequencies and intensities. The proposed model allowed us to associate the basal firing rates with the physiological characteristics of the different auditory nerve fibers. This is especially important since some noise-associated hearing losses, such as acoustic trauma, have been explained as selective fiber damages.Clinical Relevance- Models that describe the properties of auditory nerve fibers are important to study specific aspects of maturation as well as the causes of sensorineural hearing loss in humans.

Electrical Cochlear Response Consistency from different Cochlear Implant Users.

The Electrical Cochlear Response (ECR) is a scalp potential recently described in the literature which offers an alternative approach for objective adaptation of Cochlear Implant (CI) to individual patient requirements. Thus it is necessary to know about the consistency of this response across implanted patients using devices with different design criteria. This work shows that the ECR wave shape morphology is not affected by CI manufacture design differences. For this purpose and to contend with the sensibility to electric stimulation change along the cochlea, six contiguous intracochlear electrodes located at the apical end of the cochlea were studied. According to the CI manufacturer, the population of twelve implanted pediatric patients was divided into three groups. Artifacts due to the CI stimulation pip tone and operation during ECR acquisition were canceled using the Empirical Mode Decomposition method. For wave shape morphology comparison among electrodes, ECR amplitude was normalized, and the average intra- and inter-user group ECR Correlations were calculated. Intra and inter-group Correlation coefficient goes from 0.58 to 0.9 and from 0.63 to 0.85, respectively. For the same patient and group Correlation coefficient between ECR of the electrode located at the apical end of the cochlea and adjacent electrodes decreases from apex to base. These results support the consistency of the ECR waveshape morphology across users of different CI types.Clinical Relevance- ECR offers a new objective methodology for the initial programming and later readjustment of electrical stimulation provided by the cochlear implant. The patient uses the device in daily operation mode; the scenery is quite impossible with the current resources for evaluating CI performance. This methodology is compatible with all current CIs without special hardware or software requirements due to different devices type. It can be applied any time after initial device programming, regardless of patient age or previous training. Therefore, it is important to know that ECR wave shape morphology is not affected by the differences in design and operation of current cochlear stimulation systems.

Cross section of the 96Zr(α,n)99Mo reaction induced by α-particles beams on natZr targets.

The excitation function of the 96Zr (α,n)99Mo reaction was determined using the stacked-foil activation technique. For the experiments, two stacks with metal foils of Cu, Ti and Zr of natural isotopic composition were irradiated independently with a 27.2 MeV α-particle beam. The characteristics of the primary beam and its verification along each stack were determined according to the well-known natCu(α,x)65Zn, natCu(α,x)66,67Ga, and natTi (α,x)51Cr monitor reactions. It was deduced that the expected production yield from 99Mo by irradiating 96Zr targets with a 23.8 MeV alpha particle beam for 1 h is 1.77 MBq/µA. According to the results, irradiation characteristics are proposed to produce 99Mo with high specific activity.

Simulation of the efficiency of inner hair cell secretion in the auditory pathway.

Sound coding involves several stages of processing along the auditory path. Specifically, the Inner Hair Cells (IHC) act as sensory receptors and transduce acoustic information -frequency, intensity and duration of the stimulus- into neuronal signals. In this work, a stochastic model was implemented to achieve a better understanding of the IHC-auditory nerve synapse, specifically, the process of Ready Releasable Pool (RRP) vesicle exocytosis, a complicated process to study experimentally because current protocols do not provide adequate temporal resolution, in the order of milliseconds. The presented model allows predicting the efficiency of glutamate release towards explaining maturation changes or disease impacts in the auditory pathway.

Cochlear implant artifact reduction on one channel Mismatch Negativity recordings based on Ensemble Empirical Mode Decomposition and Independent Component Analysis.

Artifact generated by cochlear implants has been a problem for being able to register Mismatch Negativity (MMN) response. There are methods for reducing the artifact using multiple channels from the EEG but in this paper are presented the first results of a method using only the channel with the artifact using Ensemble Empirical Mode Decomposition (EEMD) and Independent Component Analysis (ICA). The first results showed that it was possible to get the MMN registers from the group of normal recordings and partially with the group of recordings from patients with cochlear implant. It is possible to suggest that EEMD in conjunction with ICA can be used for studies searching MMN.

A complete duplication of X chromosome resulting in a tricentric isochromosome originated by centromere repositioning.

BACKGROUND: Neocentromeres are rare and considered chromosomal aberrations, because a non-centromeric region evolves in an active centromere by mutation. The literature reported several structural anomalies of X chromosome and they influence the female reproductive capacity or are associated to Turner syndrome in the presence of monosomy X cell line. CASE PRESENTATION: We report a case of chromosome X complex rearrangement found in a prenatal diagnosis. The fetal karyotype showed a mosaicism with a 45,X cell line and a 46 chromosomes second line with a big marker, instead of a sex chromosome. The marker morphology and fluorescence in situ hybridization (FISH) characterization allowed us to identify a tricentric X chromosome constituted by two complete X chromosome fused at the p arms telomere and an active neocentromere in the middle, at the union of the two Xp arms, where usually are the telomeric regions. FISH also showed the presence of a paracentric inversion of both Xp arms. Furthermore, fragility figures were found in 56% of metaphases from peripheral blood lymphocytes culture at birth: a shorter marker chromosome and an apparently acentric fragment frequently lost. CONCLUSIONS: At our knowledge, this is the first isochromosome of an entire non-acrocentric chromosome. The neocentromere is constituted by canonical sequences but localized in an unusual position and the original centromeres are inactivated. We speculated that marker chromosome was the result of a double rearrangement: firstly, a paracentric inversion which involved the Xp arm, shifting a part of the centromere at the p end and subsequently a duplication of the entire X chromosome, which gave rise to an isochromosome. It is possible to suppose that the first event could be a result of a non-allelic homologous recombination mediated by inverted low-copy repeats. As expected, our case shows a Turner phenotype with mild facial features and no major skeletal deformity, normal psychomotor development and a spontaneous development of puberty and menarche, although with irregular menses since the last follow-up.

Vascular expression of Notch pathway receptors and ligands is restricted to arterial vessels.

Mice with targeted mutations in genes required for Notch signal transduction die during embryogenesis, displaying overt signs of hemorrhage due to defects in their vascular development. Surprisingly, directed expression of a constitutively active form of Notch4 within mouse endothelial cells produces a similar vascular embryonic lethality. Moreover, patients with mutations in Notch3 exhibit the cerebral vascular disorder, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). These findings underscore the importance of Notch signaling in vascular development; however, they do not identify the specific functional defect. Here, we report that Notch1, Notch3, Notch4, Delta4, Jagged1 and Jagged2 are all expressed in arteries, but are not expressed by veins. These findings identify an aspect of Notch signaling that could contribute to the mechanism by which this pathway modulates vascular morphogenesis.

An assessment strategy for proposals of engineering projects in the Bachelor of Biomedical Engineering Curriculum at Universidad Autónoma Metropolitana-Iztapalapa.

Since 1974, the Bachelor of Biomedical Engineering Program (BBME) is offered at Universidad Autónoma Metropolitana-Iztapalapa, in Mexico City. By design, it must be completed in four years (12 trimesters) and, in the latter three, the senior students work on a BME project, which is done by completing three modules: Project Seminar (PS), Project on BME I and Project on BME II. In the PS module, the student must find a problem of interest in the BME field and suggest a solution through the development of an Engineering Project Proposal (EPP). Currently, the module is being taught by two faculty members of the BBME, who instruct students on how to develop their EPPs and evaluate their progress by reviewing a number of EPPs during the trimester. This generates a huge workload for the module instructors, which makes it necessary to involve more faculty members trimester-to-trimester (i.e. every 12 weeks) and, therefore, to create a set of systematic guidelines that ease the evaluation process for new instructors. Hence, the purpose of this paper is to present an assessment strategy (in the form of an assessment matrix) for the PS module as well as some preliminary results after two trimesters of its implementation.

Comparison between different similarity measure functions for optimal clustering AEPs Independent Components.

A critical part of applying Independent Component Analysis (ICA) to any neurophysiological data is the selection of relevant independent Components (ICs); i. e., to decide which ICs have neurological meaning. Standard ICA implementation supposes a square mixing matrix; this results in as many ICs as EEG channels. In this work, responses to repetitive auditory stimuli are the most important signals (Auditory Evoked Potentials, AEPs); so the ICs of interest should be repetitive and time-locked with the stimuli. In this paper an update of a previously proposed procedure for the objective selection of ICs using Mutual Information (MI) and cluster analysis is presented. This time, four different similarity functions are evaluated and three inter/intra-cluster quality criteria are explored to determine optimal cluster numbers to both synthetic AEPs and data from normal hearing children, so that to identify ICs related with the auditory response. The numbers of clusters and the similarity function that yield best results in both datasets, in other words optimal clustering AEPs ICs, were 8 and Euclidean link-clustering average respectively.

Prevalence of PPD positivity among new employees at a hospital in New York City.

OBJECTIVE: To determine the prevalence of tuberculin reactivity among all new employees at a hospital in New York City. DESIGNS: Prospective measurement of purified protein derivative (PPD) status in consecutive new employees at a hospital in New York City from 1991 to 1993. All employees are tested as part of a preemployment physical, assuring complete compliance. Aplisol (Parke-Davis, Morris Plains, NJ) was used in 1991 and 1992, and Tubersol (Connaught, Swiftwater, PA) in 1993. Tests were applied and interpreted by trained employee health personnel. RESULTS: Of 313 consecutive new employees, comprising all job categories, 40% were PPD positive at time of initial hire, including 20% of US-born and 70% of foreign-born employees. Of 114 persons who had received BCG vaccination, 67% were PPD positive. By multivariate regression analysis, age, BCG vaccination history, and foreign country of birth were independent predictors of a reactive PPD test. CONCLUSIONS: The high prevalence of tuberculin reactivity may reflect high rates of Mycobacterium tuberculosis infection and disease in the community, complicating interpretation of the efficacy of Centers for Disease Control and Prevention (CDC) guidelines to prevent the spread of tuberculosis in healthcare facilities.

Benefit of two-step PPD testing of new employees at a New York City hospital.

BACKGROUND: Recent concern about nosocomial transmission of tuberculosis has led hospitals to scrutinize employee tuberculin conversion rates. The Centers for Disease Control and Prevention recommends two-step testing of new employees to limit the booster phenomenon. The cost of such a program and its subsequent yield have not recently been examined. METHODS: Employee health records were retrospectively reviewed of persons hired from 1993 and 1994 at St. Clare's Hospital in New York City, all of whom received two-step testing at time of initial employment. RESULTS: Of 262 new employees, 107 (41%) had positive tuberculin results on initial testing. The results of 15 (9.7%) of the remaining 155 patients became positive on two-step testing administered 1 week later. Persons with a positive second test result were significantly more likely to be male or foreign born or to have received previous bacille Calmette-Guérin vaccination. Identification of these 15 persons and exclusion of them from probable subsequent conversion prevented an almost 50% increase in the annual conversion rate at our hospital, from 3.2% to 4.7%. CONCLUSION: Two-step tuberculin testing is an essential means of identifying persons with a baseline positive tuberculin test result, thus allowing accurate reporting of subsequent employee tuberculin conversions.

Hepatitis B vaccination program at a New York City hospital: seroprevalence, seroconversion, and declination.

BACKGROUND: Despite implementation of hepatitis B vaccination programs, 2 problems have prevented full vaccine-induced protection of health care workers (HCWs). About 10% to 12% of vaccinated HCWs do not develop antibody, and many HCWs continue to decline vaccination. To determine the effectiveness of our hepatitis B vaccine program, we studied rates of postvaccination seroconversion and vaccine declination. METHODS: Employee health service records were used to determine demographic features, hepatitis B surface antibody serostatus at baseline, serologic response to vaccine, and declination or acceptance of vaccine. RESULTS: About 26% of HCWs were seropositive at baseline, including those vaccinated before employment. Higher seroprevalence rates were seen among those born outside the United States, nurses, and laboratory workers. Seroconversion occurred in only 79% of HCWs who completed a 3-vaccine series. Increasing age was the only significant risk for failure to convert. Declination rates overall were about 45% and were lowest in HCWs who have jobs that included potential exposure to blood. CONCLUSION: Hepatitis B seroprevalence among HCWs at our hospital is higher than in many other urban hospitals in the United States; over postvaccination seroconversion rate is substantially lower; and our declination rate of 45% resembles other published series. Declination of vaccine and failure to respond to vaccine continue to thwart achievement of full control of this preventable occupational infection.

Carbon monoxide contributes to the cytokine-induced inhibition of surfactant synthesis by human type II pneumocytes.

BACKGROUND: An increase in cyclic guanosine 3',5'-monophosphate (cGMP) due to nitric oxide generation is known to participate in the mediation of the tumor necrosis factor alpha (TNF-alpha) effect in type II cells. Because guanylyl cyclase can be activated also by carbon monoxide (CO), in this study we examined the ability of human type II pneumocytes to produce CO in the presence of cytokines and the relative contribution of this molecule to the TNF-alpha and interleukin 1 effects. DESIGN: Type II pneumocytes were isolated from cadaveric multiple-organ donors by enzymatic digestion, adherence separation of macrophages, and gradient purification. After preculture for 24 hours, cells were cultured for 24 hours in the presence or absence of TNF-alpha, interleukin 1, sodium nitroprusside, N(omega)-nitro-1-arginine, CO, hemin, zinc-protoporphyrin type IX, deferoxamine mesylate, S-adenosyl-L-methionine, alpha-tocopherol, methylene blue (a guanylyl cyclase inhibitor), 8-bromine-cGMP, and combinations of these reagents. Both CO (picomole per microgram of protein) and nitric oxide release to the medium and the cGMP (picomole per microgram of protein) content of the cells were measured. In a different set of experiments, D-glucose labeled with radioactive carbon (14C) was added to the medium, and the labeling of several lipid fractions was determined (picomole per microgram of protein). RESULTS: D-[14C]glucose incorporation into phosphatidylcholine, the main surfactant component, was selectively inhibited in the presence of cytokines, CO, sodium nitroprusside, or 8-bromine-cGMP. The inhibitory effect of TNF-alpha was partially reversed by N(omega)-nitro-L-arginine, deferoxamine, or alpha-tocopherol and totally reversed by methylene blue. Tumor necrosis factor alpha induced an increase in cGMP cell content and in the CO and nitric oxide release to the medium. Hemin increased CO and cGMP production and decreased phosphatidylcholine synthesis. Zinc-protoporphyrin type IX, an inhibitor of heme oxygenase, and all 3 antioxidants, which inhibited CO production, also antagonized the TNF-alpha effect on cGMP and phosphatidylcholine synthesis. CONCLUSIONS: Intracellular cGMP increase due to an endogenous generation of both CO and nitric oxide mediates the cytokine-induced inhibition of surfactant synthesis by type II pneumocytes. Both lipid peroxidation and heme oxygenase activity are sources for the observed CO production.

Evidence for a cyclic guanosine monophosphate-dependent, carbon monoxide-mediated, signaling system in the regulation of TNF-alpha production by human pulmonary macrophages.

BACKGROUND AND OBJECTIVES: The second messenger cyclic guanosine 3',5'-monophosphate (cGMP) seems to be implicated in the release of tumor necrosis factor alpha (TNF-alpha) by activated macrophages. There is controversy regarding the potential of human macrophages to produce nitric oxide (NO). Since guanylate cyclase can be activated also by carbon monoxide (CO) and this gas may be formed endogenously, we examined the ability of human pulmonary macrophages to produce CO in the presence of lipopolysaccharide (LPS) or LPS+interferon gamma (IFN-gamma). In addition, the source and the relative contribution of this molecule to the LPS-induced increase in cell cGMP content and TNF-alpha release were explored. DESIGN: Interstitial macrophages were obtained from multiple organ donor lungs by enzymatic digestion. After 24-hour preculture, purified macrophages were cultured for 24 hours in the presence or absence of LPS, LPS+IFN-gamma, CO (250 and 500 mumol/L), sodium nitroprusside, 8-Br-cGMP, hemoglobin, methylene blue, zinc-protoporphyrin IX, hemin, S-adenosylmethionine, deferoxamine mesylate, or combinations. The cGMP content of the cells and TNF-alpha, CO, and NO release to the medium were determined. RESULTS: In the presence of LPS, TNF-alpha production was not accompanied by any detectable increase in the NO release to the medium. However, an increase in medium CO concentration (mean +/- SEM) (5.81 +/- 0.20 vs 3.74 +/- 0.08 pmol/microgram protein; n = 11; P < .01) and cell cGMP content (0.273 +/- 0.021 vs 0.138 +/- 0.019 pmol/microgram protein; n = 10; P < .01) was observed. These changes were more pronounced in the presence of LPS+IFN-gamma. Release of TNF-alpha also was induced by both sodium nitroprusside and 8-Br-cGMP. In contrast, methylene blue, a guanylate cyclase inhibitor, inhibited LPS-, LPS+IFN-gamma-, and sodium nitroprusside-induced TNF-alpha production and cGMP increase; hemoglobin, which traps CO, had a similar effect. CONCLUSION: Intracellular cGMP increase, secondary to an endogenous production of CO, participates in the release of TNF-alpha by activated human pulmonary macrophages.

Differences in antigen expression within and between 10 isolates of Giardia duodenalis.

In this study indirect immunofluorescence was performed on both live and fixed trophozoites to determine the level of variability in surface antigen expression between 14 Giardia duodenalis isolates, using a monoclonal antibody raised against the Portland 1 isolate (ATCC No. 30888). Subsets of antigen positive cells were detected in 13 isolates ranging in number from < 1% to 50% of the total population. The differences in antigen expression between 10 uncloned isolates did not correlate with genetic differences determined using isoenzyme analysis. Examination of four clones of the Portland 1 isolate showed that all of the progeny expressed surface antigen at significantly different levels to the parent.