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Bumblebees have become model organisms for cognitive ecology and social learning. Quantifying the foraging behavior of free-flying bees, however, remains a methodological challenge. We describe and provide the code for a method of studying bee free flying foraging behavior using the open source neural-network based markerless tracking software DeepLabCut. From videos of bees foraging in an arena we trained a neural network to accurately track the position of each bee. We then used this approach to study foraging behavior and show that the ratio between flying time and flower visiting time decreases over repeated foraging bouts, indicating increasing efficiency of bee foraging behavior with experience. Visit durations, a laborious metric to measure by hand, were significantly shorter on flowers that had previously been visited. This experiment illustrates the usefulness of DeepLabCut for objective quantification of behavior, and in this case study shows that previous experience increases bee foraging efficiency. [ABSTRACT FROM AUTHOR]

Introduction: In parallel with the obesity and diabetes epidemics, steatotic liver disease (SLD) has emerged as a major global public health concern. The mainstay of therapy is counseling on weight loss and increased exercise. However, such lifestyle modifications infrequently lead to success. We aimed to identify barriers to diet and lifestyle modification in patients with SLD. Methods: Patients with SLD completed a 14-item questionnaire that assigned barriers to healthy eating to three categories: lack of knowledge, lack of self-control, and lack of time, with a higher summary score indicating more perceived barriers. We administered assessments of health literacy and physical activity. We analyzed the data using descriptive statistics and ordinal regression analysis. Results: We included 151 participants with a median age of 64; 54% were female and 68.2% were Hispanic. Median BMI was 31.9 kg/m2. Most respondents, 68.2%, had low health literacy and were either underactive, 29.1% or sedentary, 23.2%. Lack of self-control was the strongest barrier to achieving a healthy lifestyle, followed by lack of knowledge. Lack of time was not significant barrier. Patients with the most significant barriers were more likely to have obesity, low health literacy, and be sedentary. Discussion: Lack of self-control and knowledge are the greatest barriers to adopting a healthy lifestyle in patients with SLD. Future clinical interventions should integrate education that targets various health literacy levels with behavioral approaches to improve a sense of agency. [ABSTRACT FROM AUTHOR]

Plant secondary metabolites that defend leaves from herbivores also occur in floral nectar. While specialist herbivores often have adaptations providing resistance to these compounds in leaves, many social insect pollinators are generalists, and therefore are not expected to be as resistant to such compounds. The milkweeds, Asclepias spp., contain toxic cardenolides in all tissues including floral nectar. We compared the concentrations and identities of cardenolides between tissues of the North American common milkweed Asclepias syriaca, and then studied the effect of the predominant cardenolide in nectar, glycosylated aspecioside, on an abundant pollinator. We show that a generalist bumblebee, Bombus impatiens, a common pollinator in eastern North America, consumes less nectar with experimental addition of ouabain (a standard cardenolide derived from Apocynacid plants native to east Africa) but not with addition of glycosylated aspecioside from milkweeds. At a concentration matching that of the maximum in the natural range, both cardenolides reduced activity levels of bees after four days of consumption, demonstrating toxicity despite variation in behavioral deterrence (i.e., consumption). In vitro enzymatic assays of Na+/K+-ATPase, the target site of cardenolides, showed lower toxicity of the milkweed cardenolide than ouabain for B. impatiens, indicating that the lower deterrence may be due to greater tolerance to glycosylated aspecioside. In contrast, there was no difference between the two cardenolides in toxicity to the Na+/K+-ATPase from a control insect, the fruit fly Drosophila melanogaster. Accordingly, this work reveals that even generalist pollinators such as B. impatiens may have adaptations to reduce the toxicity of specific plant secondary metabolites that occur in nectar, despite visiting flowers from a wide variety of plants over the colony's lifespan. [ABSTRACT FROM AUTHOR]

Hepatitis B (HBV) is endemic in Haiti, therefore Haitian immigrants should be screened to identify and link affected individuals to care. Current screening approaches are ineffective. We assessed the acceptability and feasibility of home-based screening among Haitian immigrants using community health workers (CHWs). We recruited participants exiting a pragmatic trial evaluating strategies to improve care delivery (NCT02970136). Participants completed an acceptability questionnaire. Blood drawn by CHWs at participants' homes or community sites was tested for hepatitis B surface antigen, hepatitis B surface antibody and hepatitis B core antibody. Of 60 participants, 59 found screening acceptable; 53 had blood drawn. Of those, 45.3% had HBV previously, 49.1% remained susceptible and 5.7% were vaccinated. Respondents cited various reasons community members might find screening unacceptable. The high prior HBV rate highlights the need for effective outreach programs. Home-based HBV screening was both acceptable and feasible among Haitian immigrants. [ABSTRACT FROM AUTHOR]

Purpose: Hepatitis B (HBV), the leading cause of hepatocellular carcinoma (HCC), disproportionately affects minorities. Compared to other races, Blacks more often present with advanced HCC and have decreased survival. We observed higher HBV-associated HCC rates among Blacks than reported nationally. In our center, Haitian Blacks had the highest rates of HBV-associated HCC and shorter survival compared to other Blacks. We investigated knowledge and perceptions regarding HBV and HCC among Blacks born in the United States or Haiti. Methods: Using community partnerships, participants were recruited via word of mouth, email, social media or from Hepatology clinic. Focus groups were conducted in Haitian Creole or English and stratified by birthplace, gender and infection status. Discussions were audio-recorded and transcribed verbatim. A constant comparative method was used for data analysis; themes are based on conversational details. Results: There were 55 participants; 49% were male and 27% had chronic HBV. Only 42% of Haitian Blacks knew about HBV prior to participation vs. 78% of African Americans, p 0.03. Both groups expressed that fear, mistrust of the medical establishment, denial and stigma might compel persons to avoid seeking care. Both groups attributed higher rates of late stage HCC diagnosis in Blacks to inadequate financial resources and education. Those with HBV reported confusion regarding their infection and suboptimal communication with healthcare providers. Conclusions: In two communities disproportionately affected by HBV, misconceptions about disease transmission, stigma, low health literacy and decreased access to care may limit detection for HBV. Culturally relevant community-based interventions are needed to increase HBV detection. [ABSTRACT FROM AUTHOR]

Background: Hepatitis B (HBV), the leading cause of hepatocellular carcinoma (HCC) worldwide, disproportionately affects minorities in the USA. Undiagnosed HBV precludes HCC screening and contributes to late-stage cancer presentation and decreased survival. Barriers to HBV and HCC screening include lack of insurance and limited diffusion of guidelines. We aimed to assess knowledge about HBV and HCC screening indications and explore barriers to screening.Methods: We surveyed trainees from the University of Miami/Jackson Memorial Hospitals, Palmetto General Hospital, and Mount Sinai Medical Center. We assessed knowledge using clinical vignettes. We performed bivariate and Chi-squared analyses.Results: There were 183 respondents; median age was 31 and 52% were male. The sample was 35% Hispanic, 29% White, 18% Asian, and 9% Black. Training department was Internal Medicine, 71%; Family Medicine, 11%; Infectious Diseases, 6%; or Gastroenterology, 7%. Only 59% correctly estimated national HBV prevalence; 25% correctly estimated global prevalence. In vignettes with behavioral risk factors, trainees correctly advised screening, 63-96%. However, when the risk factor was the birthplace, correct responses ranged from 33 to 53%. Overall, 45% chose an incorrect combination of HBV screening tests. Perceived barriers to screening included limited expertise in screening of immigrants and limited patient education. Respondents were more likely to recommend HCC screening in cirrhotic patients versus non-cirrhotic HBV patients. Key barriers to HCC screening included uncertainty about HCC guidelines and patient financial barriers.Conclusions: Knowledge of HBV and HCC screening recommendations is suboptimal among trainees. Efforts to broadly disseminate HBV and HCC guidelines through targeted educational interventions are needed. [ABSTRACT FROM AUTHOR]

Plant suspension culture is attracting interest as a promising platform to produce biological medicines due to the absence of virus, prions or DNA related to mammals during the production process. However, the heterogenic plant cell proliferation nature is particularly challenging for establishing industrial processes based on innovative approaches currently used, particularly in the animal cell culture industry. In this context, while Process Analytical Technology (PAT) tools have been used to monitor classical parameters such as biomass dry weight, its use in cells heterogeneity has received limited attention. Therefore, the feasibility of in situ monitoring of cell differentiation in plant cell suspensions employing NIR spectroscopy and chemometrics was investigated. Off-line measurements of cell heterogeneity in term of cell differentiation and in-line NIR spectra captured in 3 L bioreactor cultures were employed to generate calibration models. Then models were tested to estimate the population distribution of parenchyma, collenchyma and sclerenchyma cells during Catharanthus roseus suspension cultures. Results have proven in situ NIR spectroscopy as a capable PAT tool to monitor differentiated cells accurately and in real-time. These results are the starting point to follow-up PAT systems so that plant cell culture heterogeneity may be better understood and controlled in biopharmaceutical plant cell cultures. [ABSTRACT FROM AUTHOR]

Monarch butterflies, Danaus plexippus, migrate long distances over which they encounter host plants that vary broadly in toxic cardenolides. Remarkably little is understood about the mechanisms of sequestration in Lepidoptera that lay eggs on host plants ranging in such toxins. Using closely-related milkweed host plants that differ more than ten-fold in cardenolide concentrations, we mechanistically address the intake, sequestration, and excretion of cardenolides by monarchs. We show that on high cardenolide plant species, adult butterflies saturate in cardenolides, resulting in lower concentrations than in leaves, while on low cardenolide plants, butterflies concentrate toxins. Butterflies appear to focus their sequestration on particular compounds, as the diversity of cardenolides is highest in plant leaves, lower in frass, and least in adult butterflies. Among the variety of cardenolides produced by the plant, sequestered compounds may be less toxic to the butterflies themselves, as they are more polar on average than those in leaves. In accordance with this, results from an in vitro assay based on inhibition of Na+/K+ ATPase (the physiological target of cardenolides) showed that on two milkweed species, including the high cardenolide A. perennis, extracts from butterflies have lower inhibitory effects than leaves when standardized by cardenolide concentration, indicating selective sequestration of less toxic compounds from these host plants. To understand how ontogeny shapes sequestration, we examined cardenolide concentrations in caterpillar body tissues and hemolymph over the course of development. Caterpillars sequestered higher concentrations of cardenolides as early instars than as late instars, but within the fifth instar, concentration increased with body mass. Although it appears that large amounts of sequestration occurs in early instars, a host switching experiment revealed that caterpillars can compensate for feeding on low cardenolide host plants with substantial sequestration in the fifth instar. We highlight commonalities and striking differences in the mechanisms of sequestration depending on host plant chemistry and developmental stage, which have important implications for monarch defense. [ABSTRACT FROM AUTHOR]

Background and Aims: Hepatocellular carcinoma (HCC) incidence is increasing at differential rates depending on race. We aimed to identify associations between race and survival after HCC diagnosis in a diverse American population.Methods: Using the cancer registry from Sylvester Comprehensive Cancer Center, University of Miami and Jackson Memorial Hospitals, we performed retrospective analysis of 999 patients diagnosed with HCC between 9/24/2004 and 12/19/2014. We identified clinical characteristics by reviewing available electronic medical records. The association between race and survival was analyzed using Cox proportional hazards regression.Results: Median survival in days was 425 in Blacks, 904.5 in non-Hispanic Whites, 652 in Hispanics, 570 in Asians, and 928 in others, p < 0.01. Blacks and Asians presented at more advanced stages with larger tumors. Although Whites had increased severity of liver disease at diagnosis compared to other races, they had 36% reduced rate of death compared to Blacks, [hazard ratio (HR) 0.64, 95% confidence interval (CI) 0.51-0.8, p < 0.01]. After adjusting for significant covariates, Whites had 22% (HR 0.78, 95% CI 0.61-0.99, p 0.04) reduced risk of death, compared to Blacks. Transplant significantly reduced rate of death; however, only 13.3% of Blacks had liver transplant, compared to 40.1% of Whites, p < 0.01.Conclusions: In this diverse sample of patients, survival among Blacks is the shortest after HCC diagnosis. Survival differences reflect a more advanced tumor stage at presentation rather than severity of underlying liver disease precluding treatment. Improving survival in minority populations, in whom HCC incidence is rapidly increasing, requires identification and modification of factors contributing to late-stage presentation. [ABSTRACT FROM AUTHOR]

Purpose: To assess the impact of the duration and intensity of episodes of increased intracranial pressure on 6-month neurological outcome in adult and paediatric traumatic brain injury. Methods: Analysis of prospectively collected minute-by-minute intracranial pressure and mean arterial blood pressure data of 261 adult and 99 paediatric traumatic brain injury patients from multiple European centres. The relationship of episodes of elevated intracranial pressure (defined as a pressure above a certain threshold during a certain time) with 6-month Glasgow Outcome Scale was visualized in a colour-coded plot. Results: The colour-coded plot illustrates the intuitive concept that episodes of higher intracranial pressure can only be tolerated for shorter durations: the curve that delineates the duration and intensity of those intracranial pressure episodes associated with worse outcome is an approximately exponential decay curve. In children, the curve resembles that of adults, but the delineation between episodes associated with worse outcome occurs at lower intracranial pressure thresholds. Intracranial pressures above 20 mmHg lasting longer than 37 min in adults, and longer than 8 min in children, are associated with worse outcomes. In a multivariate model, together with known baseline risk factors for outcome in severe traumatic brain injury, the cumulative intracranial pressure-time burden is independently associated with mortality. When cerebrovascular autoregulation, assessed with the low-frequency autoregulation index, is impaired, the ability to tolerate elevated intracranial pressures is reduced. When the cerebral perfusion pressure is below 50 mmHg, all intracranial pressure insults, regardless of duration, are associated with worse outcome. Conclusions: The intracranial pressure-time burden associated with worse outcome is visualised in a colour-coded plot. In children, secondary injury occurs at lower intracranial pressure thresholds as compared to adults. Impaired cerebrovascular autoregulation reduces the ability to tolerate intracranial pressure insults. Thus, 50 mmHg might be the lower acceptable threshold for cerebral perfusion pressure. [ABSTRACT FROM AUTHOR]

From its 1960 beginnings in a pair of windowless Genetics Department laboratories under the Stanford Medical School Dean's Office to its current broad-based program, which joins faculty members from departments across the Medical School, the Stanford Immunology Program has played a central role in shaping both basic and clinical immunology thinking. In this article, we tell the story of the beginnings of this odyssey in a reminiscence-based format that brings the flavor of the time in the words of people who lived and built the history. [ABSTRACT FROM AUTHOR]

The fringe-lipped bat, Trachops cirrhosus, is an eavesdropping predator that hunts frogs and katydids by approaching these preys' sexual advertisement calls. In captivity, bats can rapidly learn to associate novel acoustic stimuli with food rewards. It is unknown how this learning ability is related to foraging behavior in the wild where prey and the calls that identify them vary over space and time. In two bat populations that differ in available prey species (Soberanía, Panama, and La Selva, Costa Rica), we presented wild-caught bats with frog calls, katydid calls, and control stimuli. Bats in Soberanía were significantly more responsive to complex calls and choruses of the túngara frog, Physalaemus pustulosus, than were bats in La Selva. La Selva bats were significantly more responsive to katydid calls (Steirodon sp.) than Soberanía bats. We also examined seasonal variation in bat response to prey cues. Bats were captured in Soberanía in dry and wet seasons and presented with the calls of a dry season breeding frog ( Smilisca sila), a wet season breeding frog ( P. pustulosus), and four katydid species. Bats captured in the dry season were significantly more responsive to the calls of S. sila than bats captured in the wet season, but there were no seasonal differences in response to the calls of P. pustulosus or the katydid calls. We demonstrate plasticity in the foraging behavior of this eavesdropping predator but also show that response to prey cues is not predicted solely by prey availability. [ABSTRACT FROM AUTHOR]

The mating calls of male túngara frogs, Physalaemus pustulosus, attract intended (conspecific females) and unintended (eavesdropping predators and parasites) receivers. The calls are complex, having two components: a frequency-modulated 'whine' followed by 0-7 harmonic bursts or 'chucks'. The whine is necessary and sufficient to elicit phonotaxis from females and the chuck enhances call attractiveness when it follows a whine. Although chucks are never made alone, females perceptually bind the whine and chuck when they are spatially separated. We tested whether an unintended receiver with independent evolution of phonotaxis, the frog-eating bat, Trachops cirrhosus, has converged with frogs in its auditory grouping of the call components. In contrast to frogs, bats approached chucks broadcast alone; when the chuck was spatially separated from the whine the bats preferentially approached the whine, and bats were sensitive to whine-chuck temporal sequence. This contrast suggests that although disparate taxa may be selected to respond to the same signals, different evolutionary histories, selective regimes, and neural and cognitive architectures may result in different weighting and grouping of signal components between generalist predators and conspecific mates. [ABSTRACT FROM AUTHOR]

Eavesdropping on prey communication signals has never before been reported for a Palearctic bat species. In this study, we investigated whether lesser and greater mouse-eared bats, Myotis blythii oxygnathus and Myotis myotis, find tettigoniid bushcrickets (Tettigoniidae) by eavesdropping on their mate-attraction song. Tettigoniids are known to be the most important prey item for M. blythii oxygnathus, while carabid beetles and other epigaeic arthropods are the most important prey for its sibling species, M. myotis, in many places in Europe. M. myotis locates walking beetles by listening for their rustling sounds. We compared these two species' response to four acoustic prey cues: calling song of two tettigoniid species, the rustling sound made by walking carabid beetles, and a control tone. Individuals of both bat species attacked the speaker playing tettigoniid song, which clearly indicates that both species eavesdrop on prey-generated advertisement signals. There were, however, species differences in response. M. blythii oxygnathus exhibited stronger predatory responses to the calling song of two species of tettigoniid than to the beetle rustling sound or the control. M. myotis, in contrast, exhibited stronger predatory responses to the beetle rustling and to one tettigoniid species but not the other tettigoniid or the control. Our study (1) for the first time demonstrates eavesdropping on prey communication signals for Palearctic bats and (2) gives preliminary evidence for sensory niche partitioning between these two sympatric sibling bat species. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between stuttering and speaking rates in a 4 year-old male child who stuttered and the child's mother during conversations. A single-subject experimental time-series design (ABCDA) was used to investigate the effect of decreasing the speaking rates of both the mother and the child on stuttering. Decreasing speaking rates of both the mother and child produced a decrease in the stuttering rate of the child, not accompanied by reductions in either linguistic complexity or frequency of interruption. The diminished stuttering observed during manipulation generalized to other speaking situations. [ABSTRACT FROM AUTHOR]

Enterprise integration research focuses on the development and integration of models with the goal of analysis and improvement of an enterprise. Cognitive engineering research focuses on the problem solving requirements of humans in complex systems with the goal of designing more effective systems. This paper presents a particular approach to cognitive engineering - model-based intelligent support - and draws implications to the design and development of enterprise models and tools. Specifically, we discuss the realm of distributed supervisory control, propose a knowledge architecture and theory of human - machine interaction to support cooperative problem solving, and link this to current enterprise integration research. Examples are drawn from the spacecraft operations domain. [ABSTRACT FROM AUTHOR]

Our studies of the origins of the nonfunctional E and E genes and their associated A genes have provided a unique view of the factors affecting the evolution of these genes and their haplotypes. The set of three haplotypes originating in M. m. domesticus and M. m. castaneus carrying E genes with the identical E mutation allows a direct comparison between the rates of divergence of the non-expressed (E) genes and the linked expressed (A) genes. The near-identity of the three E genes and the divergence of the A1 domains provides strong evidence that selection acting on functional class II proteins is a major driving force in the accumulation and maintenance of MHC polymorphism. The basis for the retention of null E and E genes at high frequencies as balanced polymorphisms in mouse populations remains difficult to understand, given the expectation that E phenotypes should result in reduced immune response potential. However, the high frequencies of E haplotypes and the maintenance of specific mutant E and E genes since their origin prior to the divergence of M. m. domesticus from M. m. castaneus and bactrianus suggest that these nonfunctional alleles are being actively maintained. It may be that in some pathogenic environments the expression of EE proteins is selected against, due to E-associated immune-mediated pathology or reductions in the functional T-cell repertoire. [ABSTRACT FROM AUTHOR]

The Global Oscillation Network Group (GONG) Project is planning to place a set of instruments around the world to observe solar oscillations as continuously as possible for at last three years. The Project has now chosen the sites that will comprise the network. This paper describes the methods of data collection and analysis that were used to make this decision. Solar irradiance data were collected with a one-minute cadence at fifteen sites around the world and analyzed to produce statistics of cloud cover, atmospheric extinction, and transparency power spectra at the individual sites. Nearly 200 reasonable six-site networks were assembled from the individual stations, and a set of statistical measures of the performance of the networks was analyzed using a principal component analysis. An accompanying paper presents the results of the survey. [ABSTRACT FROM AUTHOR]

Given the extensive allelic amino acid sequence polymorphism present in the first domain of A, A, and E chains and its profound effects on class II function, the minimal polymorphism in the mouse E chain (and in its human homologue DR) is paradox. Two possible explanations for the lack of polymorphism in E are: (1) the E chain plays such a uniquely critical structural/functional role in antigen presentation, T-cell activation, repertoire selection, and/or pairing with E or other proteins for expression that it cannot vary, and mutations are selected against; (2) the E chain plays a less significant role than the outer domains of other major histocompatibility complex (MHC) proteins in determining the interactions with processed peptides or with T-cell receptor (TCR), so there is no selective pressure to maintain new mutations. To explore this question we compared the ability of transfectants expressing wild type (wt) EE and mutant E wt E proteins to present peptides and bacterial superantigens to T-cell hybridomas. Mutations at the E amino acid positions 31, 52, and 65&66, to residues that represent allelic alternatives in A chains, significantly reduced activation of peptide-specific T hybridomas, and mutations at 71 sometimes enhanced T-cell stimulation. None of the E mutations reduced, and some enhanced, superantigen stimulation of T-cell hybridomas. These results argue against the hypothesis that E chains are minimally polymorphic because mutations in E are functionally neutral. [ABSTRACT FROM AUTHOR]

Molecular and biochemical techniques have been used to explore the reasons behind low E chain expression in the EEI-region recombinant strain, A.TFR5. A.TFR5 ( A E, ap5), a recombinant between A.CA ( A E) and A.TL ( A E), carries the E subregion. Previous results have shown that it expresses the E chain, but at reduced levels relative to EEstrains. No E chains were detected, which is consistent with the A.TFR5 E gene being derived from the A.CA parent, which carries the null Eallele. In this paper, the defect in E-chain expression is explored. Restriction fragment length polymorphism analysis has localized the recombination event in A.TFR5 approximately 30 kb upstream of E, in the region of the large intervening sequence of E. Northern blot analysis of total RNA from A.TFR5 shows normal amounts of the E message, but no E message. Two-dimensional gel analysis of 15 min pulse-labeled A.TFR5, A.CA, and A.TL E immunoprecipitates shows decreased levels of the intracellular E chain in A.TFR5 relative to A.TL. However, analysis of total cell extracts shows normal levels of this protein. A glycoprotein fraction isolated from total cell extracts of 5 h labeled cells contains normal amounts of intracellular E, but decreased amounts of the mature cell-surface protein. These data suggest that in the absence of E, the E chain (1) takes on an altered conformation that is not as efficiently recognized by alloantibodies, and (2) is found in normal levels as the partially glycosylated intracellular precursor, but is not processed and/or transported efficiently to the cell surface. [ABSTRACT FROM AUTHOR]

Hamster alloantisera and a monoclonal antibody originally generated against antigens controlled by the murine I-E subregion, which cross-reacts with hamster cell surface antigens, have been used to define two distinct Ia-like complexes in the Syrian hamster. These complexes have been named α: β and α: β and are detected by hamster alloantisera or monoclonal antibody 14-4-4, respectively. For the three strains studied, α: β, appears to be polymorphic in both α and β chains, while the α: β complex is nonpolymorphic, as revealed by 2-D PAGE analyses. A third nonpolymorphic glycoprotein that appears to be the hamster's equivalent of the murine invariant chain (I) is associated with both the α: β and α: β complexes. In addition, we report the first biochemical detection of polymorphism between the closely related CB and MHA Syrian hamster strains. [ABSTRACT FROM AUTHOR]

The genetic and molecular requirements for cell-surface expression of Ia antigens precipitated by anti- I-E subregion sera have been examined. Inbred mice of the d, k, p, and r haplotypes synthesize and express on their lymphocytes the two I-region products normally found in anti- I-E-subregion immunoprecipitates, E and A (E). Cells from mice of the b and s haplotypes fail to synthesize E chains but do synthesize A chains, which remain in the cytoplasm as partially glycosylated precursors. Cells of the f and q haplotypes fail to synthesize either the A or E polypeptide chains, as shown by both genetic complementation tests and analyses of total cell proteins by two-dimensional polyacrylamide gel electrophoresis. The patterns of expression of the intact E:A complex are consistent with the theory that both the A and E polypeptide chains must be present in the cells for either chain to be expressed in normal amounts on the cell surface. The implications of these observations for the genetics of I-region-controlled functions are discussed. [ABSTRACT FROM AUTHOR]