Do bed bugs transmit human viruses, or do humans spread bed bugs and their viruses? A worldwide survey of the bed bug RNA virosphere

BED BUGS: (Hemiptera: Cimicidae) are a globally distributed hematophagous pest that routinely feed on humans. Unlike many blood-sucking arthropods, they have never been linked to pathogen transmission in a natural setting, and despite increasing interest in their role as disease vectors, little is known about the viruses that bed bugs naturally harbor. Here, we present a global-scale survey of the bed bug RNA virosphere. We sequenced the metatranscriptomes of 22 individual bed bugs (Cimex lectularius and Cimex hemipterus) from 8 locations around the world. We detected sequences from two known bed bug viruses (Shuangao bedbug virus 1 and Shuangao bedbug virus 2) which extends their geographical range. We identified three novel bed bug virus sequences from a tenui-like virus (Bunyavirales), a toti-like virus (Ghabrivirales), and a luteo-like virus (Tolivirales). Interestingly, some of the bed bug viruses branch near to insect-transmitted plant-infecting viruses, opening questions regarding the evolution of plant virus infection. When we analyzed the viral sequences by their host's collection location, we found unexpected patterns of geographical diversity that may reflect humans' role in bed bug dispersal. Additionally, we investigated the effect that Wolbachia, the primary bed bug endosymbiont, may have on viral abundance and found that Wolbachia infection neither promotes nor inhibits viral infection. Finally, our results provide no evidence that bed bugs transmit any known human pathogenic viruses.

Ex vivo characterization of the circulating hemocytes of bed bugs and their responses to bacterial exposure

Bed bugs (Cimex spp.) are urban pests of global importance. Knowledge of the immune system of bed bugs has implications for understanding their susceptibility to biological control agents, their potential to transmit human pathogens, and the basic comparative immunology of insects. Nonetheless, the immunological repertoire of the family Cimicidae remains poorly characterized. Here, we use microscopy, flow cytometry, and RNA sequencing to provide a basal characterization of the circulating hemocytes of the common bed bug, Cimex lectularius. We also examine the responses of these specialized cells to E. coli exposure using the same techniques. Our results show that circulating hemocytes are comprised of at least four morphologically distinct cell types that are capable of phagocytosis, undergo degranulation, and exhibit additional markers of activation following stimulation, including size shift and DNA replication. Furthermore, transcriptomic profiling reveals expression of predicted Toll/IMD signaling pathway components, antimicrobial effectors and other potentially immunoresponsive genes in these cells. Together, our data demonstrate the conservation of several canonical cellular immune responses in the common bed bug and provide a foundation for additional mechanistic immunological studies with specific pathogens of interest.

Developmental and comparative perspectives on mosquito immunity

Diseases spread by mosquitoes have killed more people than those spread by any other group of arthropod vectors and remain an important factor in determining global health and economic stability. The mosquito innate immune system can act to either modulate infection with human pathogens or fight off entomopathogens and increase the fitness and longevity of infected mosquitoes. While work remains towards understanding the larval immune system and the development of the mosquito immune system, it has recently become clearer that environmental factors heavily shape the developing mosquito immune system and continue to influence the adult immune system as well. The adult immune system has been well-studied and is known to involve multiple tissues and diverse molecular mechanisms. This review summarizes and synthesizes what is currently understood about the development of the mosquito immune system and includes comparisons of immune components unique to mosquitoes among the blood-feeding arthropods as well as important distinguishing factors between the anopheline and culicine mosquitoes. An explanation is included for how mosquito immunity factors into vector competence and vectorial capacity is presented along with a model for the interrelationships between nutrition, microbiome, pathogen interactions and behavior as they relate to mosquito development, immune status, adult female fitness and ultimately, vectorial capacity. Novel discoveries in the fields of mosquito ecoimmunology, neuroimmunology, and intracellular antiviral responses are highlighted.

The Selection of a Hepatocyte Cell Line Susceptible to Plasmodium falciparum Sporozoite Invasion That Is Associated With Expression of Glypican-3

In vitro studies of liver stage (LS) development of the human malaria parasite Plasmodium falciparum are technically challenging; therefore, fundamental questions about hepatocyte receptors for invasion that can be targeted to prevent infection remain unanswered. To identify novel receptors and to further understand human hepatocyte susceptibility to P. falciparum sporozoite invasion, we created an optimized in vitro system by mimicking in vivo liver conditions and using the subcloned HC-04.J7 cell line that supports mean infection rates of 3-5% and early development of P. falciparum exoerythrocytic forms-a 3- to 5-fold improvement on current in vitro hepatocarcinoma models for P. falciparum invasion. We juxtaposed this invasion-susceptible cell line with an invasion-resistant cell line (HepG2) and performed comparative proteomics and RNA-seq analyses to identify host cell surface molecules and pathways important for sporozoite invasion of host cells. We identified and investigated a hepatocyte cell surface heparan sulfate proteoglycan, glypican-3, as a putative mediator of sporozoite invasion. We also noted the involvement of pathways that implicate the importance of the metabolic state of the hepatocyte in supporting LS development. Our study highlights important features of hepatocyte biology, and specifically the potential role of glypican-3, in mediating P. falciparum sporozoite invasion. Additionally, it establishes a simple in vitro system to study the LS with improved invasion efficiency. This work paves the way for the greater malaria and liver biology communities to explore fundamental questions of hepatocyte-pathogen interactions and extend the system to other human malaria parasite species, like P. vivax.

Whole genome sequence of two Rathayibacter toxicus strains reveals a tunicamycin biosynthetic cluster similar to Streptomyces chartreusis

Rathayibacter toxicus is a forage grass associated Gram-positive bacterium of major concern to food safety and agriculture. This species is listed by USDA-APHIS as a plant pathogen select agent because it produces a tunicamycin-like toxin that is lethal to livestock and may be vectored by nematode species native to the U.S. The complete genomes of two strains of R. toxicus, including the type strain FH-79, were sequenced and analyzed in comparison with all available, complete R. toxicus genomes. Genome sizes ranged from 2,343,780 to 2,394,755 nucleotides, with 2079 to 2137 predicted open reading frames; all four strains showed remarkable synteny over nearly the entire genome, with only a small transposed region. A cluster of genes with similarity to the tunicamycin biosynthetic cluster from Streptomyces chartreusis was identified. The tunicamycin gene cluster (TGC) in R. toxicus contained 14 genes in two transcriptional units, with all of the functional elements for tunicamycin biosynthesis present. The TGC had a significantly lower GC content (52%) than the rest of the genome (61.5%), suggesting that the TGC may have originated from a horizontal transfer event. Further analysis indicated numerous remnants of other potential horizontal transfer events are present in the genome. In addition to the TGC, genes potentially associated with carotenoid and exopolysaccharide production, bacteriocins and secondary metabolites were identified. A CRISPR array is evident. There were relatively few plant-associated cell-wall hydrolyzing enzymes, but there were numerous secreted serine proteases that share sequence homology to the pathogenicity-associated protein Pat-1 of Clavibacter michiganensis. Overall, the genome provides clear insight into the possible mechanisms for toxin production in R. toxicus, providing a basis for future genetic approaches.

Plasmodium falciparum CRK4 directs continuous rounds of DNA replication during schizogony

Plasmodium parasites, the causative agents of malaria, have evolved a unique cell division cycle in the clinically relevant asexual blood-stage of infection¹. DNA replication commences approximately halfway through the intracellular development following invasion and parasite growth. The schizont stage is associated with multiple rounds of DNA replication and nuclear division without cytokinesis resulting in a multinucleated cell. Nuclei divide asynchronously through schizogony, with only the final round of DNA replication and segregation being synchronous and coordinated with daughter cell assembly^2,3. However, the control mechanisms for this divergent mode of replication are unknown. Here we show that the Plasmodium-specific kinase PfCRK4 is a key cell cycle regulator that orchestrates the multiple rounds of DNA replication throughout schizogony in P. falciparum. PfCRK4 depletion led to a complete block in nuclear division and profoundly inhibited DNA replication. Quantitative phosphoproteomic profiling identified a set of PfCRK4-regulated phosphoproteins with greatest functional similarity to CDK2 substrates, particularly proteins involved in origin of replication firing. PfCRK4 was required for the initial and subsequent rounds of DNA replication during schizogony, and in addition was essential for development in the mosquito vector. Our results identified an essential S phase promoting factor of the unconventional P. falciparum cell cycle. PfCRK4 is required for both a prolonged period of the intraerythrocytic blood-stage of malaria infection, as well as for transmission, revealing a broad window for PfCRK4-targeted chemotherapeutics.

A Malaria Transmission-Blocking (+)-Usnic Acid Derivative Prevents Plasmodium Zygote-to-Ookinete Maturation in the Mosquito Midgut

The evolution of drug resistance is a recurrent problem that has plagued efforts to treat and control malaria. Recent emergence of artemisinin resistance in Southeast Asia underscores the need to develop novel antimalarials and identify new targetable pathways in Plasmodium parasites. Transmission-blocking approaches, which typically target gametocytes in the host bloodstream or parasite stages in the mosquito gut, are recognized collectively as a strategy that when used in combination with antimalarials that target erythrocytic stages will not only cure malaria but will also prevent subsequent transmission. We tested four derivatives of (+)-usnic acid, a metabolite isolated from lichens, for transmission-blocking activity against Plasmodium falciparum using the standard membrane feeding assay. For two of the derivatives, BT37 and BT122, we observed a consistent dose-response relationship between concentration in the blood meal and oocyst intensity in the midgut. To explore their mechanism of action, we used the murine model Plasmodium berghei and found that both derivatives prevent ookinete maturation. Using fluorescence microscopy, we demonstrated that in the presence of each compound zygote vitality was severely affected, and those that did survive failed to elongate and mature into ookinetes. The observed phenotypes were similar to those described for mutants of specific kinases (NEK2/NEK4) and of inner membrane complex 1 (IMC1) proteins, which are all vital to the zygote-to-ookinete transition. We discuss the implications of our findings and our high-throughput screening approach to identifying next generation, transmission-blocking antimalarials based on the scaffolds of these (+)-usnic acid derivatives.

Molecular Profiling of Phagocytic Immune Cells in Anopheles gambiae Reveals Integral Roles for Hemocytes in Mosquito Innate Immunity

The innate immune response is highly conserved across all eukaryotes and has been studied in great detail in several model organisms. Hemocytes, the primary immune cell population in mosquitoes, are important components of the mosquito innate immune response, yet critical aspects of their biology have remained uncharacterized. Using a novel method of enrichment, we isolated phagocytic granulocytes and quantified their proteomes by mass spectrometry. The data demonstrate that phagocytosis, blood-feeding, and Plasmodium falciparum infection promote dramatic shifts in the proteomic profiles of An. gambiae granulocyte populations. Of interest, large numbers of immune proteins were induced in response to blood feeding alone, suggesting that granulocytes have an integral role in priming the mosquito immune system for pathogen challenge. In addition, we identify several granulocyte proteins with putative roles as membrane receptors, cell signaling, or immune components that when silenced, have either positive or negative effects on malaria parasite survival. Integrating existing hemocyte transcriptional profiles, we also compare differences in hemocyte transcript and protein expression to provide new insight into hemocyte gene regulation and discuss the potential that post-transcriptional regulation may be an important component of hemocyte gene expression. These data represent a significant advancement in mosquito hemocyte biology, providing the first comprehensive proteomic profiling of mosquito phagocytic granulocytes during homeostasis blood-feeding, and pathogen challenge. Together, these findings extend current knowledge to further illustrate the importance of hemocytes in shaping mosquito innate immunity and their principal role in defining malaria parasite survival in the mosquito host.

The fucomic potential of mosquitoes: Fucosylated N-glycan epitopes and their cognate fucosyltransferases

Fucoconjugates are key mediators of protein-glycan interactions in prokaryotes and eukaryotes. As examples, N-glycans modified with the non-mammalian core α1,3-linked fucose have been detected in various organisms ranging from plants to insects and are immunogenic in mammals. The rabbit polyclonal antibody raised against plant horseradish peroxidase (anti-HRP) is able to recognize the α1,3-linked fucose epitope and is also known to specifically stain neural tissues in the fruit fly Drosophila melanogaster. In this study, we have detected and localized the anti-HRP cross-reactivity in another insect species, the malaria mosquito vector Anopheles gambiae. We were able to identify and structurally elucidate fucosylated N-glycans including core mono- and difucosylated structures (responsible for anti-HRP cross reactivity) as well as a Lewis-type antennal modification on mosquito anionic N-glycans by applying enzymatic and chemical treatments. The three mosquito fucosyltransferase open reading frames (FucT6, FucTA and FucTC) required for the in vivo biosynthesis of the fucosylated N-glycan epitopes were identified in the Anopheles gambiae genome, cloned and recombinantly expressed in Pichia pastoris. Using a robust MALDI-TOF MS approach, we characterised the activity of the three recombinant fucosyltransferases in vitro and demonstrate that they share similar enzymatic properties as compared to their homologues from D. melanogaster and Apis mellifera. Thus, not only do we confirm the neural reactivity of anti-HRP in a mosquito species, but also demonstrate enzymatic activity for all its α1,3- and α1,6-fucosyltransferase homologues, whose specificity matches the results of glycomic analyses.

Sex-partitioning of the Plasmodium falciparum stage V gametocyte proteome provides insight into falciparum-specific cell biology

One of the critical gaps in malaria transmission biology and surveillance is our lack of knowledge about Plasmodium falciparum gametocyte biology, especially sexual dimorphic development and how sex ratios that may influence transmission from the human to the mosquito. Dissecting this process has been hampered by the lack of sex-specific protein markers for the circulating, mature stage V gametocytes. The current evidence suggests a high degree of conservation in gametocyte gene complement across Plasmodium, and therefore presumably for sex-specific genes as well. To better our understanding of gametocyte development and subsequent infectiousness to mosquitoes, we undertook a Systematic Subtractive Bioinformatic analysis (filtering) approach to identify sex-specific P. falciparum NF54 protein markers based on a comparison with the Dd2 strain, which is defective in producing males, and with syntenic male and female proteins from the reanalyzed and updated P. berghei (related rodent malaria parasite) gametocyte proteomes. This produced a short list of 174 male- and 258 female-enriched P. falciparum stage V proteins, some of which appear to be under strong diversifying selection, suggesting ongoing adaptation to mosquito vector species. We generated antibodies against three putative female-specific gametocyte stage V proteins in P. falciparum and confirmed either conserved sex-specificity or the lack of cross-species sex-partitioning. Finally, our study provides not only an additional resource for mass spectrometry-derived evidence for gametocyte proteins but also lays down the foundation for rational screening and development of novel sex-partitioned protein biomarkers and transmission-blocking vaccine candidates.

The acute transcriptomic and proteomic response of HC-04 hepatoma cells to hepatocyte growth factor and its implications for Plasmodium falciparum sporozoite invasion

The routine study of human malaria liver-stage biology in vitro is hampered by low infection efficiency of human hepatocellular carcinoma (HCC) lines (<0.1%), poor understanding of steady-state HCC biology, and lack of appropriate tools for trace sample analysis. HC-04 is the only HCC that supports complete development of human malaria parasites. We hypothesized that HCCs are in various intermediate stages of the epithelial-mesenchymal transition (EMT) and HC-04s retain epithelial characteristics that permit infection. We developed a facile analytical approach to test this hypothesis viz. the HC-04 response to hepatocyte growth factor (HGF). We used online two-dimensional liquid chromatography tandem mass spectrometry (2D-LC-MS/MS) to quantify protein expression profiles in HC-04 pre-/post-HGF treatment and validated these results by RT-qPCR and microscopy. We successfully increased protein identification efficiency over offline-2D methods by 12-fold, using less sample material, allowing robust protein quantification. We observed expected up-regulation and down-regulation of EMT protein markers in response to HGF, but also unexpected cellular responses. We also observed that HC-04 is generally more susceptible to HGF-mediated signaling than what was observed for HepG2, a widely used, but poor malaria liver stage-HCC model. Our analytical approach to understanding the basic biology of HC-04 helps us understand the factors that may influence its utility as a model for malaria liver-stage development. We observed that HC-04 treatment with HGF prior to the addition of Plasmodium falciparum sporozoites did not facilitate cell invasion, which suggests unlinking the effect of HGF on malaria liver stage development from hepatocyte invasion. Finally, our 2D-LC-MS/MS approach and broadly applicable experimental strategy should prove useful in the analysis of various hepatocyte-pathogen interactions, tumor progression, and early disease events.

Spatial and temporal in vivo analysis of circulating and sessile immune cells in mosquitoes: hemocyte mitosis following infection

Background

Mosquitoes respond to infection by mounting immune responses. The primary regulators of these immune responses are cells called hemocytes, which kill pathogens via phagocytosis and via the production of soluble antimicrobial factors. Mosquito hemocytes are circulated throughout the hemocoel (body cavity) by the swift flow of hemolymph (blood), and data show that some hemocytes also exist as sessile cells that are attached to tissues. The purpose of this study was to create a quantitative physical map of hemocyte distribution in the mosquito, Anopheles gambiae, and to describe the cellular immune response in an organismal context.

Results

Using correlative imaging methods we found that the number of hemocytes in a mosquito decreases with age, but that regardless of age, approximately 75% of the hemocytes occur in circulation and 25% occur as sessile cells. Infection induces an increase in the number of hemocytes, and tubulin and nuclear staining showed that this increase is primarily due to mitosis and, more specifically, autonomous cell division, by circulating granulocytes. The majority of sessile hemocytes are present on the abdominal wall, although significant numbers of hemocytes are also present in the thorax, head, and several of the appendages. Within the abdominal wall, the areas of highest hemocyte density are the periostial regions (regions surrounding the valves of the heart, or ostia), which are ideal locations for pathogen capture as these are areas of high hemolymph flow.

Conclusions

These data describe the spatial and temporal distribution of mosquito hemocytes, and map the cellular response to infection throughout the hemocoel.

Infection-induced interaction between the mosquito circulatory and immune systems

Insects counter infection with innate immune responses that rely on cells called hemocytes. Hemocytes exist in association with the insect's open circulatory system and this mode of existence has likely influenced the organization and control of anti-pathogen immune responses. Previous studies reported that pathogens in the mosquito body cavity (hemocoel) accumulate on the surface of the heart. Using novel cell staining, microdissection and intravital imaging techniques, we investigated the mechanism of pathogen accumulation in the pericardium of the malaria mosquito, Anopheles gambiae, and discovered a novel insect immune tissue, herein named periostial hemocytes, that sequesters pathogens as they flow with the hemolymph. Specifically, we show that there are two types of endocytic cells that flank the heart: periostial hemocytes and pericardial cells. Resident periostial hemocytes engage in the rapid phagocytosis of pathogens, and during the course of a bacterial or Plasmodium infection, circulating hemocytes migrate to the periostial regions where they bind the cardiac musculature and each other, and continue the phagocytosis of invaders. Periostial hemocyte aggregation occurs in a time- and infection dose-dependent manner, and once this immune process is triggered, the number of periostial hemocytes remains elevated for the lifetime of the mosquito. Finally, the soluble immune elicitors peptidoglycan and β-1,3-glucan also induce periostial hemocyte aggregation, indicating that this is a generalized and basal immune response that is induced by diverse immune stimuli. These data describe a novel insect cellular immune response that fundamentally relies on the physiological interaction between the insect circulatory and immune systems.

Mosquitoes transmit diseases such as malaria, dengue fever, West Nile virus and lymphatic filariasis. A mosquito initially acquires a pathogen when she ingests a blood meal from an infected person or animal. Then, after a period of development and/or replication in the mosquito gut, the pathogen enters the hemocoel (body cavity) and undergoes an obligate migration to the salivary glands (the destination for viruses and protozoans) or the mouthparts (the destination for larger worms). During this migration, pathogens are subject to two potentially antagonistic mosquito forces: immune responses and circulatory currents. In this study, we examined the physiological interactions between the mosquito immune and circulatory systems. We show that when mosquitoes are infected with bacteria or malaria parasites, mosquito immune cells (hemocytes) migrate to the areas surrounding the valves of the heart. At these areas of rapid and dynamic hemolymph (mosquito blood) flow, hemocytes swiftly phagocytose and kill pathogens. These experiments describe a novel and basal insect immune response that fundamentally relies on the physiological interaction between the mosquito circulatory and immune system. Furthermore, because traversal of the hemocoel is required for pathogen transmission, this new knowledge could be used in the development of novel disease control strategies.

The evolutionary imprint of domestication on genome variation and function of the filamentous fungus Aspergillus oryzae

The domestication of animals, plants, and microbes fundamentally transformed the lifestyle and demography of the human species [1]. Although the genetic and functional underpinnings of animal and plant domestication are well understood, little is known about microbe domestication [2-6]. Here, we systematically examined genome-wide sequence and functional variation between the domesticated fungus Aspergillus oryzae, whose saccharification abilities humans have harnessed for thousands of years to produce sake, soy sauce, and miso from starch-rich grains, and its wild relative A. flavus, a potentially toxigenic plant and animal pathogen [7]. We discovered dramatic changes in the sequence variation and abundance profiles of genes and wholesale primary and secondary metabolic pathways between domesticated and wild relative isolates during growth on rice. Our data suggest that, through selection by humans, an atoxigenic lineage of A. flavus gradually evolved into a "cell factory" for enzymes and metabolites involved in the saccharification process. These results suggest that whereas animal and plant domestication was largely driven by Neolithic "genetic tinkering" of developmental pathways, microbe domestication was driven by extensive remodeling of metabolism.

Complex effects of temperature on mosquito immune function

Over the last 20 years, ecological immunology has provided much insight into how environmental factors shape host immunity and host–parasite interactions. Currently, the application of this thinking to the study of mosquito immunology has been limited. Mechanistic investigations are nearly always conducted under one set of conditions, yet vectors and parasites associate in a variable world. We highlight how environmental temperature shapes cellular and humoral immune responses (melanization, phagocytosis and transcription of immune genes) in the malaria vector, Anopheles stephensi. Nitric oxide synthase expression peaked at 30°C, cecropin expression showed no main effect of temperature and humoral melanization, and phagocytosis and defensin expression peaked around 18°C. Further, immune responses did not simply scale with temperature, but showed complex interactions between temperature, time and nature of immune challenge. Thus, immune patterns observed under one set of conditions provide little basis for predicting patterns under even marginally different conditions. These quantitative and qualitative effects of temperature have largely been overlooked in vector biology but have significant implications for extrapolating natural/transgenic resistance mechanisms from laboratory to field and for the efficacy of various vector control tools.

Members of the salivary gland surface protein (SGS) family are major immunogenic components of mosquito saliva

Mosquitoes transmit Plasmodium and certain arboviruses during blood feeding, when they are injected along with saliva. Mosquito saliva interferes with the host's hemostasis and inflammation response and influences the transmission success of some pathogens. One family of mosquito salivary gland proteins, named SGS, is composed of large bacterial-type proteins that in Aedes aegypti were implicated as receptors for Plasmodium on the basal salivary gland surface. Here, we characterize the biology of two SGSs in the malaria mosquito, Anopheles gambiae, and demonstrate their involvement in blood feeding. Western blots and RT-PCR showed that Sgs4 and Sgs5 are produced exclusively in female salivary glands, that expression increases with age and after blood feeding, and that protein levels fluctuate in a circadian manner. Immunohistochemistry showed that SGSs are present in the acinar cells of the distal lateral lobes and in the salivary ducts of the proximal lobes. SDS-PAGE, Western blots, bite blots, and immunization via mosquito bites showed that SGSs are highly immunogenic and form major components of mosquito saliva. Last, Western and bioinformatic analyses suggest that SGSs are secreted via a non-classical pathway that involves cleavage into a 300-kDa soluble fragment and a smaller membrane-bound fragment. Combined, these data strongly suggest that SGSs play an important role in blood feeding. Together with their role in malaria transmission, we propose that SGSs could be used as markers of human exposure to mosquito bites and in the development of disease control strategies.

Contraction of the ventral abdomen potentiates extracardiac retrograde hemolymph propulsion in the mosquito hemocoel

BACKGROUND

Hemolymph circulation in mosquitoes is primarily controlled by the contractile action of a dorsal vessel that runs underneath the dorsal midline and is subdivided into a thoracic aorta and an abdominal heart. Wave-like peristaltic contractions of the heart alternate in propelling hemolymph in anterograde and retrograde directions, where it empties into the hemocoel at the terminal ends of the insect. During our analyses of hemolymph propulsion in Anopheles gambiae, we observed periodic ventral abdominal contractions and hypothesized that they promote extracardiac hemolymph circulation in the abdominal hemocoel.

METHODOLOGY/PRINCIPAL FINDINGS

We devised methods to simultaneously analyze both heart and abdominal contractions, as well as to measure hemolymph flow in the abdominal hemocoel. Qualitative and quantitative analyses revealed that ventral abdominal contractions occur as series of bursts that propagate in the retrograde direction. Periods of ventral abdominal contraction begin only during periods of anterograde heart contraction and end immediately following a heartbeat directional reversal, suggesting that ventral abdominal contractions function to propel extracardiac hemolymph in the retrograde direction. To test this functional role, fluorescent microspheres were intrathoracically injected and their trajectory tracked throughout the hemocoel. Quantitative measurements of microsphere movement in extracardiac regions of the abdominal cavity showed that during periods of abdominal contractions hemolymph flows in dorsal and retrograde directions at a higher velocity and with greater acceleration than during periods of abdominal rest. Histochemical staining of the abdominal musculature then revealed that ventral abdominal contractions result from the contraction of intrasegmental lateral muscle fibers, intersegmental ventral muscle bands, and the ventral transverse muscles that form the ventral diaphragm.

CONCLUSIONS/SIGNIFICANCE

These data show that abdominal contractions potentiate extracardiac retrograde hemolymph propulsion in the abdominal hemocoel during periods of anterograde heart flow.

Structural mechanics of the mosquito heart and its function in bidirectional hemolymph transport

The insect circulatory system transports nutrients, signaling molecules, wastes and immune factors to all areas of the body. The primary organ driving circulation is the dorsal vessel, which consists of an abdominal heart and a thoracic aorta. Here, we present qualitative and quantitative data characterizing the heart of the mosquito, Anopheles gambiae. Visual observation showed that the heart of resting mosquitoes contracts at a rate of 1.37 Hz (82 beats per minute) and switches contraction direction, with 72% of contractions occurring in the anterograde direction (toward the head) and 28% of contractions occurring in the retrograde direction (toward the tip of the abdomen). The heart is tethered to the midline of the abdominal tergum by six complete and three incomplete pairs of alary muscles, and propels hemolymph at an average velocity of 8 mm s−1 by sequentially contracting muscle fibers oriented in a helical twist with respect to the lumen of the vessel. Hemolymph enters the heart through six pairs of incurrent abdominal ostia and one pair of ostia located at the thoraco-abdominal junction that receive hemolymph from the abdominal hemocoel and thoracic venous channels, respectively. The vessel expels hemolymph through distal excurrent openings located at the anterior end of the aorta and the posterior end of the heart. In conclusion, this study presents a comprehensive revision and expansion of our knowledge of the mosquito heart and for the first time quantifies hemolymph flow in an insect while observing dorsal vessel contractions.

Inhibition of human brain tumor cell growth by the anti-inflammatory drug, flurbiprofen

Despite many efforts to alter the relentlessly aggressive progression of tumors of neural origin, individuals bearing these tumors exhibit poor prognosis for long-term survival. In an attempt to find an effective treatment, we examined the efficacy of the non-steroidal anti-inflammatory drug, flurbiprofen, to suppress the growth of tumor cell lines derived from medulloblastoma and glioblastoma multiforme. Results from cell proliferation assays have revealed that flurbiprofen effectively inhibits the growth of various tumor cells in a dose-dependent manner and causes a noticeable change in the progression of cells through cell cycle stages. Treatment of tumor cells with flurbiprofen reduced the number of cells in G1 and G2, and significantly increased their numbers in S phase, suggesting that, flurbiprofen accelerates G1/S entry, and/or delays cell exit from S to G2/M stages. Results from RNase protection assay and Western blot analysis showed that while treatment of cells with flurbiprofen causes a minor change in the RNA level of different cyclins, there is a significant decrease in the level of cyclin B protein upon flurbiprofen treatment. Examination of tumor suppressors by RNase protection technique showed a subtle increase in the levels of several tumor suppressors upon flurbiprofen treatment. Interestingly, at the protein level, p53 tumor suppressor was substantially increased upon flurbiprofen treatment, yet the level of p21, a downstream target for p53 remained unchanged. Curiously, treatment of the cells with flurbiprofen enhanced the level of COX-2 expression. Results from co-immunoprecipitation showed association of COX-2 with p53 in tumor cells. These observations suggest that the interaction of COX-2 with p53 may cause p21-independent suppression of tumor cell growth upon flurbiprofen treatment.

Selective, unilateral, reversible loss of behavioral responses to looming stimuli after injection of tetrodotoxin of cadmium chloride into the frog optic nerve

Unilateral injection of tetrodotoxin or cadmium chloride into the frog optic nerve selectively eliminates behavioral responses to looming stimuli while sparing responses to prey stimuli. This behavioral loss is correlated with a loss of activity of "dimming" units in tectal layer G. These findings suggest that separate sets of retinal ganglion cell fibers carry information concerning looming stimuli and prey stimuli. The lack of activity in layer G suggests that information about looming stimuli is being conveyed by myelinated retinal ganglion cell axons. It is argued that unmyelinated fibers are not blocked by the neurotoxins because the extracellular space around the fibers is mostly inaccessible.

Evaluating the sale of a nonprofit health system to a for-profit hospital management company: the Legacy Experience

OBJECTIVE

To introduce and develop a decision model that can be used by the leadership of nonprofit healthcare organizations to assist them in evaluating whether selling to a for-profit organization is in their community's best interest.

STUDY SETTING/DATA SOURCES

A case study of the planning process and decision model that Legacy Health System used to evaluate whether to sell to a for-profit hospital management company and use the proceeds of the sale to establish a community health foundation. Data sources included financial statements of benchmark organizations, internal company records, and numerous existing studies.

STUDY DESIGN

The development of the multivariate model was based on insight gathered through a review of the current literature regarding the conversion of nonprofit healthcare organizations.

DATA COLLECTION/EXTRACTION METHODS

The effect that conversion from nonprofit to for-profit status would have on each variable was estimated based on assumptions drawn from the current literature and on an analysis of Legacy and for-profit hospital company data.

PRINCIPAL FINDINGS

The results of the decision model calculations indicate that the sale of Legacy to a for-profit firm and the subsequent creation of a community foundation would have a negative effect on the local community.

CONCLUSIONS

The use of the decision model enabled senior management and trustees to systematically address the conversion question and to conclude that continuing to operate as a nonprofit organization would provide the most benefit to the local community. The model will prove useful to organizations that decide to sell to a for-profit organization as well as those that choose to continue nonprofit operations. For those that decide to sell, the model will assist in minimizing any potential negative effect that conversion may have on the community. The model will help those who choose not to sell to develop a better understanding of the organization's value to the community.

Time responses of cancellous and cortical bones to sciatic neurectomy in growing female rats

Effects of unilateral sciatic neurectomy on the responses of both cancellous and cortical bones were studied in growing female rats at 0, 1, 4, 8, and 12 weeks after operation. Using double-fluorescent labeling techniques, histomorphometric analyses were performed on longitudinal sections of proximal tibial metaphyseal secondary spongiosa (PTM) and on cross sections of tibial shaft (TX). In PTM, sciatic neurectomy not only inhibited the age-related bone gain, but also reduced the trabecular bone mass by 46%, which was accompanied by decreases in trabecular number, thickness, and node to node density, and an increase in trabecular separation and free end to free end density. The bone loss occurred mainly between 1 and 4 weeks after operation. A sharp increase in bone formation indices was observed during the first week after nerve section. However, these endpoints quickly dropped to levels lower than those of sham-operated controls at 4 weeks, and were not different from the control levels at 8 weeks after operation. Eroded surface increased progressively after sciatic neurectomy during the 12 weeks experimental period. In TX, sciatic neurectomy inhibited the age-related increase in total tissue area that maintained it at the basal control level. However, the cortical bone area in neurectomized legs was lower than that in sham-operated controls. Sciatic neurectomy also stimulated the bone formation indices on both periosteal and endocortical surfaces during the first week after operation. These endpoints declined sharply between 1 and 4 weeks and then maintained at control levels between 8 and 12 weeks post surgery. Endocortical eroded surface increased 1 week after neurectomy, reached the peak at 8 weeks, and then decreased thereafter. These findings suggest that (1) sciatic neurectomy not only inhibited age-related bone gain but also induced marked bone loss in cancellous bone site and inhibited age-related bone gain in cortical bone site, which mainly resulted from the decrease in bone formation and the increase in bone resorption; (2) the changes in both cancellous and cortical bones responded to sciatic neurectomy occurred mostly within the first 4 weeks and stabilized between 8 and 12 weeks after surgical intervention. In conclusion, the unilateral sciatic neurectomized rat is a complex model in which to study osteopenia. Despite sciatic neurectomy being a simple operation, the interactions of skeletal responses to postsurgical regional acceleratory phenomenon (RAP) and disuse and adaptation changes cannot be clearly differentiated. Furthermore, the complications from growth and aging should be avoided.

Endogenous natriuretic factors 3: isolation and characterization of human natriuretic factors LLU-alpha, LLU-beta 1, and LLU-gamma

A low molecular weight endogenous substance believed to be responsible for extracellular fluid homeostasis in mammals has been sought for many years. Our goal is to isolate and structurally characterize this putative "natriuretic hormone." We have developed an assay using the conscious rat to measure prolonged natriuresis (Benaksas et al (1993) Life Sciences, 52, 1045-1054), the activity originally described for this putative substance. Using this assay we have identified a number of natriuretic compounds isolated from human uremic urine. The collected urine is processed by ultrafiltration (< or = 3 kDa), gel filtration chromatography (G-25) and extraction with isopropanol and diethyl ether. The organic soluble material is then subjected to sequential high-performance liquid chromatography. We report here the initial characterization of two pure isolates (LLU-alpha and LLU-gamma) obtained by this method, and the structural elucidation of a third pure compound, LLU-beta 1, a natriuretic and previously unreported metabolite of the drug diltiazem.

Building a legacy for the future: creating an integrated health care system

Local and national market forces of decreasing inpatient utilization and increasing costs paved the way for a major merger involving five hospitals and one home health agency in Portland, Oregon. The result: a health care delivery system that merged corporate cultures, eliminated duplicity, integrated medical and administrative staffs, realized cost containment savings, and effectively responded to market trends toward reform.

Abnormalities of the breast caused by biopsy: spectrum of mammographic findings

It is important for radiologists to be familiar with the spectrum of mammographic abnormalities caused by postbiopsy changes in the breast. Although many breast biopsies leave no residual abnormality, occasionally an atypical manifestation of a biopsy scar may produce a radiologic finding suspicious enough to mandate a biopsy. Problem-solving maneuvers recommended to increase confidence that a change is related to a recent biopsy include (1) skin markers; (2) comparison with preoperative films; (3) correlation with physical examination; (4) tailored mammographic views, including focal spot compression, magnification, and tangential views; and (5) postoperative and follow-up mammograms.

1991 outlook: progress will require partnerships, improved productivity--roundtable discussion

To address the myriad problems and challenges in the next year, the operative word will be partnership. That's according to members of Modern Healthcare's editorial advisory board in their discussion of the healthcare industry in 1991. The experts see the need for hospitals, physicians and the business community to team up to control costs, solve staffing woes and take initial steps toward healthcare reform.

Determination of normal transverse mediastinal width and mediastinal-width to chest-width (M/C) ratio in control subjects: implications for subjects with aortic or brachiocephalic arterial injury

We measured transverse mediastinal width and mediastinal-width to chest-width (M/C) ratio on supine films of 100 nontraumatized controls. In 95% the transverse mediastinal width was less than 7.5 cm and the M/C ratio was less than 0.38. Thus a transverse width of 7.5 cm or more or an M/C ratio of 0.38 or more can be defined as abnormal with 95% confidence. Application of these values to determine abnormality in 32 patients with proven aortic or brachiocephalic injury showed that the transverse mediastinal width was within normal limits in 41% and M/C ratio was normal in 69%. Utilizing smaller values that would identify all abnormals resulted in false positive rates in the controls of 74% and 87%, respectively. However, one or more of eight specific signs of mediastinal abnormality related to hemorrhage or pseudoaneurysm formation were present in 94% of abnormals compared to only 11% of controls. Because of extreme overlap of transverse mediastinal width and M/C ratio between normals and abnormals, precise measurement of the mediastinum cannot reliably separate the two groups. The subjective assessment of anatomic mediastinal abnormality remains a superior plain film method in determining the need for aortography.

The potential effects of radiographic criteria to exclude aortography in patients with blunt chest trauma. Results of a study of 32 patients with proved aortic or brachiocephalic arterial injury

The purpose of this study was to test the effectiveness, in patients with known aortic or brachiocephalic arterial injury, of five previously published radiographic criteria for excluding aortography in patients with blunt chest trauma. These criteria were (1) normal findings on erect chest radiograph; (2) normal aortic arch and left subclavian artery; (3) normal aortic arch, descending aorta, aortopulmonary window, tracheal position, and left paraspinal interface; (4) normal right paratracheal stripe and nasogastric tube position, and (5) normal aortic arch and tracheal and nasogastric tube position. One or more of these criteria were met in 6% to 25% of patient with major thoracic arterial injury, depending on the criteria used. Interestingly, two (6%) patients had radiographs that showed no specific signs of mediastinal hemorrhage, which indicates that the chest radiograph is limited in its sensitivity to detect major thoracic arterial injury. Because of these results, we do not believe that attempts to limit aortography in patients with supine film evidence of mediastinal abnormality, based on the absence of certain signs of mediastinal hemorrhage, are warranted. Furthermore, an abnormal radiograph cannot be relied on as the sole criterion for aortography if the goal of care is to detect as close to 100% of vascular injuries as possible.

Acting on mission to care for the needy

Evangelical Health Systems (EHS), Chicago's largest provider of health care services, through long-range strategic planning continues to fulfill its religious-based mission of caring for the needy. By concentrating on the strengths and needs of the residents of the West and South Sides, EHS is developing programs and services to care for the elderly and poor. This article outlines key components of the system's strategy in these areas.

A religiously affiliated health care system in today's competitive market: a success story

In today's competitive health care market, not-for-profit religiously affiliated health care systems face multiple challenges for survival. Their mission of providing for the effective and efficient delivery of quality health care and health-related services for the benefit of individuals, families, and society and a philosophy of maintaining a Christian emphasis in all endeavors conflicts with many of the current competitive themes in health care. The successful system profiled here is Evangelical Health Systems (EHS), a not-for-profit organization affiliated with the United Church of Christ.

Time course of active Na transport and oxidative metabolism following transepithelial potential perturbation in toad urinary bladder

The use of an Ussing chamber with well-defined mixing characteristics coupled to a mass spectrometer permits the concurrent evaluation of transepithelial current and oxidative metabolism with improved temporal resolution. The time-course of the amiloride-sensitive current Ia and the rate of suprabasal CO2 production JsbCO2 were observed in 10 toad urinary bladders at short-circuit and after clamping delta psi at 100 mV, serosa positive. Following perturbation of delta psi (0 leads to 100 mV), Ia declined sharply within 1/2 min, remaining near constant approximately 15 min, and then increased slightly. JsbCO2 declined more gradually, remained near constant at approximately 4-7 min, and then declined further. Detailed analysis revealed an early quasi-steady state with near constancy of JsbCO2 starting at 2.9 +/- 1.1 (SD) min and lasting 4.7 +/- 1.8 (SD) min, followed by relaxation to a later steady state at about 15 min. During the early quasi-steady state, Ia was also nearly constant. Considering that in steady states Ia/F approximately or equal to JaNa, the rate of transepithelial active Na transport, during the early quasi-steady state mean values +/- SE of JaNa, JsbCO2 and (JaNa/JsbCO2) were, respectively, 29.9 +/- 1.7%, 59.4 +/- 3.2%, and 56.4 +/- 5.7% of values at short-circuit. Corresponding values during the late steady state were 41.4 +/- 6.0%, 38.2 +/- 6.1%, and 111.3 +/- 8.6%. Thus the flow ratio JaNa/JsbCO2 was depressed significantly during the early quasi-steady state, but returned later to the original value. The results of measurements of Ia and JsbO2 in three hemibladders were qualitatively similar. In terms of a phenomenological "black-box" treatment the findings are consistent with earlier studies indicating incomplete coupling between transport and metabolism. Further studies will be required to clarify the molecular basis for these observations.

A mass spectrometer to measure transepithelial unidirectional labeled water fluxes

A sealed quartz micropipette forms a liquid-vacuum interface that together with a uranium reduction element and a mass spectrometer functions as an in vitro real-time labeled water-selective microelectrode. Its performance is demonstrated by monitoring unidirectional fluxes across toad urinary bladder. This instrument has direct applicability to studies of water flux across epithelial membranes and could also be useful in monitoring water fluxes across such preparations as isolated tubules or capillaries.

A scanning micropipette molecule microscope

A movable quartz micropipette, whose tip is sealed with a polymer plug, is used as a liquid-vacuum interface to a mass spectrometer. A light microscope allows observation of, and positioning of, the micropipette tip on the surface of a sample mounted in a perfusion chamber. This forms the basis of an instrument which enables one to study, in vitro, the localization of transepithelial transport of water and other molecules. Some preliminary results from the use of this instrument are presented.

Use of mass spectrometer to measure CO2 and O2 fluxes in voltage-clamped epithelia

A quadrupole mass spectrometer was coupled to an Ussing chamber in order to evaluate rates of oxidative metabolism in voltage-clamped epithelia. Well-defined mixing characteristics of the continuously perfused chamber allowed CO2 and O2 concentrations to be related to rates of CO2 efflux, JCO2, and oxygen influx, JO2. The use of a model tissue to simulate step changes in JCO2 validated the treatment, with response within a minute. Monitoring of metabolism was facilitated by use of a desk-top computer, which evaluated JCO2 at 6-s intervals. Concurrent measurements of electrical current and JCO2 were made in the toad urinary bladder in order to relate active sodium transport to metabolism; the use of amiloride to eliminate active transport and the associated metabolism then allowed evaluation of the rates of active Na transport (JNa) and suprabasal metabolism (JsbCO2), and their ratio JNa/JsbCO2. We report the ability to resolve a 5 pmol/s change in CO2 efflux or an 11 pmol/s change in O2 influx rates.

The molecule microscope: a new instrument for biological and biomedical research

We describe a new instrument, the molecule microscope, which reveals directly spatial variations in the rate of evaporation of molecules from surfaces by using neutral molecules instead of light or charged particles used in existing kinds of microscopes. The surface composition of the sample determines the binding energy of the evaporating molecules and, hence, the rate of evaporation, which also depends on permeability of the sample when the molecules come either from within or from the other side. We show first results obtained with our apparatus, discuss the design of an instrument now under construction with approximately 1-mum resolution, and describe briefly some more advanced versions under consideration with approximately 100-A resolution.