Blood-feeding ecology of mosquitoes in two zoological gardens in the United Kingdom

BACKGROUND

Zoological gardens contain unique configurations of exotic and endemic animals and plants that create a diverse range of developing sites and potential sources of blood meals for local mosquitoes. This may imply unusual interspecific pathogen transmission risks involving zoo vertebrates, like avian malaria to captive penguins. Understanding mosquito ecology and host feeding patterns is necessary to improve mosquito control and disease prevention measures in these environments.

METHODS

Mosquito sampling took place in Chester Zoo for 3 years (2017, 2018, and 2019) and for 1 year in Flamingo Land (2017) using different trapping methods. Blood-fed mosquitoes were identified and their blood meal was amplified by PCR, sequenced, and blasted for host species identification.

RESULTS

In total, 640 blood-fed mosquitoes were collected [Culex pipiens (n = 497), Culiseta annulata (n = 81), Anopheles maculipennis s.l. (n = 7), An. claviger (n = 1), and unidentifiable (n = 55)]. Successful identification of the host species was achieved from 159 blood-fed mosquitoes. Mosquitoes fed on birds (n = 74), non-human mammals (n = 20), and humans (n = 71). There were mixed blood meals from two hosts (n = 6). The proportions of blood-fed mosquitoes varied across sampling seasons and sites within the zoos. The use of resting traps and aspiration of vegetation were more efficient techniques for capturing blood-fed mosquitoes than traps for host-seeking or gravid mosquitoes. By relating the locations of zoo vertebrates to where fed mosquitoes were trapped, the minimum travelling distances were calculated (13.7 to 366.7 m). Temperature, precipitation, relative humidity, proximity to zoo vertebrate exhibits, and vegetation level were found to be significantly associated with the proportion of captured blood-fed mosquitoes by generalized linear modelling.

CONCLUSIONS

Mosquito feeding behaviour in zoos is mainly influenced by time, location (sampling area), temperature, and host availability, which highlights the value of mosquito monitoring in complex settings to plan control strategies and potentially reduce inherent disease transmission risks for humans and threatened zoo vertebrates.

Vertebrate-Aedes aegypti and Culex quinquefasciatus (Diptera)-arbovirus transmission networks: Non-human feeding revealed by meta-barcoding and next-generation sequencing

Background

Aedes aegypti mosquito-borne viruses including Zika (ZIKV), dengue (DENV), yellow fever (YFV), and chikungunya (CHIKV) have emerged and re-emerged globally, resulting in an elevated burden of human disease. Aedes aegypti is found worldwide in tropical, sub-tropical, and temperate areas. The characterization of mosquito blood meals is essential to understand the transmission dynamics of mosquito-vectored pathogens.

Methodology/principal findings

Here, we report Ae. aegypti and Culex quinquefasciatus host feeding patterns and arbovirus transmission in Northern Mexico using a metabarcoding-like approach with next-generation deep sequencing technology. A total of 145 Ae. aegypti yielded a blood meal analysis result with 107 (73.8%) for a single vertebrate species and 38 (26.2%) for two or more. Among the single host blood meals for Ae. aegypti, 28.0% were from humans, 54.2% from dogs, 16.8% from cats, and 1.0% from tortoises. Among those with more than one species present, 65.9% were from humans and dogs. For Cx. quinquefasciatus, 388 individuals yielded information with 326 (84%) being from a single host and 63 (16.2%) being from two or more hosts. Of the single species blood meals, 77.9% were from dogs, 6.1% from chickens, 3.1% from house sparrows, 2.4% from humans, while the remaining 10.5% derived from other 12 host species. Among those which had fed on more than one species, 11% were from dogs and humans, and 89% of other host species combinations. Forage ratio analysis revealed dog as the most over-utilized host by Ae. aegypti (= 4.3) and Cx. quinquefasciatus (= 5.6) and the human blood index at 39% and 4%, respectively. A total of 2,941 host-seeking female Ae. aegypti and 3,536 Cx. quinquefasciatus mosquitoes were collected in the surveyed area. Of these, 118 Ae. aegypti pools and 37 Cx. quinquefasciatus pools were screened for seven arboviruses (ZIKV, DENV 1–4, CHIKV, and West Nile virus (WNV)) using qRT-PCR and none were positive (point prevalence = 0%). The 95%-exact upper limit confidence interval was 0.07% and 0.17% for Ae. aegypti and Cx. quinquefasciatus, respectively

Conclusions/significance

The low human blood feeding rate in Ae. aegypti, high rate of feeding on mammals by Cx. quinquefasciatus, and the potential risk to transmission dynamics of arboviruses in highly urbanized areas of Northern Mexico is discussed.

Elucidating arbovirus-vector-host contact networks is critical to understand and control mosquito-borne virus transmission, including pathogens such as ZIKV, DENV 1–4, CHIKV, and WNV. Here, we report the results of metabarcoding of blood meals of two primary pathogen mosquito vectors, Aedes aegypti and Culex quinquefasciatus. We found limited human blood feeding by Ae. aegypti and high preference for feeding on mammals by Cx. quinquefasciatus. Interestingly, blood meal analysis revealed dogs as the most utilized host for both vector species suggesting the potential for zooprophylaxis for human-amplified urban arboviruses. Pools of these vector species were tested for seven arboviruses and all were negative. We calculated vectorial capacity to discuss the potential risk and transmission dynamics of pathogens transmitted by these two important vectors in an urban location in Northern Mexico.

Critical Review of Read-Across Potential in Testing for Endocrine-Related Effects in Vertebrate Ecological Receptors

Recent regulatory testing programs have been designed to evaluate whether a chemical has the potential to interact with the endocrine system and could cause adverse effects. Some endocrine pathways are highly conserved among vertebrates, providing a potential to extrapolate data generated for one vertebrate taxonomic group to others (i.e., biological read-across). To assess the potential for biological read-across, we reviewed tools and approaches that support species extrapolation for fish, amphibians, birds, and reptiles. For each of the estrogen, androgen, thyroid, and steroidogenesis (EATS) pathways, we considered the pathway conservation across species and the responses of endocrine-sensitive endpoints. The available data show a high degree of confidence in the conservation of the hypothalamus-pituitary-gonadal axis between fish and mammals and the hypothalamus-pituitary-thyroid axis between amphibians and mammals. Comparatively, there is less empirical evidence for the conservation of other EATS pathways between other taxonomic groups, but this may be due to limited data. Although more information on sensitive pathways and endpoints would be useful, current developments in the use of molecular target sequencing similarity tools and thoughtful application of the adverse outcome pathway concept show promise for further advancement of read-across approaches for testing EATS pathways in vertebrate ecological receptors. Environ Toxicol Chem 2020;39:739-753. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Using mid-infrared spectroscopy and supervised machine-learning to identify vertebrate blood meals in the malaria vector, Anopheles arabiensis

BACKGROUND

The propensity of different Anopheles mosquitoes to bite humans instead of other vertebrates influences their capacity to transmit pathogens to humans. Unfortunately, determining proportions of mosquitoes that have fed on humans, i.e. Human Blood Index (HBI), currently requires expensive and time-consuming laboratory procedures involving enzyme-linked immunosorbent assays (ELISA) or polymerase chain reactions (PCR). Here, mid-infrared (MIR) spectroscopy and supervised machine learning are used to accurately distinguish between vertebrate blood meals in guts of malaria mosquitoes, without any molecular techniques.

METHODS

Laboratory-reared Anopheles arabiensis females were fed on humans, chickens, goats or bovines, then held for 6 to 8 h, after which they were killed and preserved in silica. The sample size was 2000 mosquitoes (500 per host species). Five individuals of each host species were enrolled to ensure genotype variability, and 100 mosquitoes fed on each. Dried mosquito abdomens were individually scanned using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectrometer to obtain high-resolution MIR spectra (4000 cm-1 to 400 cm-1). The spectral data were cleaned to compensate atmospheric water and CO2 interference bands using Bruker-OPUS software, then transferred to Python™ for supervised machine-learning to predict host species. Seven classification algorithms were trained using 90% of the spectra through several combinations of 75-25% data splits. The best performing model was used to predict identities of the remaining 10% validation spectra, which had not been used for model training or testing.

RESULTS

The logistic regression (LR) model achieved the highest accuracy, correctly predicting true vertebrate blood meal sources with overall accuracy of 98.4%. The model correctly identified 96% goat blood meals, 97% of bovine blood meals, 100% of chicken blood meals and 100% of human blood meals. Three percent of bovine blood meals were misclassified as goat, and 2% of goat blood meals misclassified as human.

CONCLUSION

Mid-infrared spectroscopy coupled with supervised machine learning can accurately identify multiple vertebrate blood meals in malaria vectors, thus potentially enabling rapid assessment of mosquito blood-feeding histories and vectorial capacities. The technique is cost-effective, fast, simple, and requires no reagents other than desiccants. However, scaling it up will require field validation of the findings and boosting relevant technical capacity in affected countries.

Barcoding blood meals: New vertebrate-specific primer sets for assigning taxonomic identities to host DNA from mosquito blood meals

The transmission dynamics of mosquito-vectored pathogens are, in part, mediated by mosquito host-feeding patterns. These patterns are elucidated using blood meal analysis, a collection of serological and molecular techniques that determine the taxonomic identities of the host animals from which blood meals are derived. Modern blood meal analyses rely on polymerase chain reaction (PCR), DNA sequencing, and bioinformatic comparisons of blood meal DNA sequences to reference databases. Ideally, primers used in blood meal analysis PCRs amplify templates from a taxonomically diverse range of vertebrates, produce a short amplicon, and avoid co-amplification of non-target templates. Few primer sets that fit these requirements are available for the cytochrome c oxidase subunit I (COI) gene, the species identification marker with the highest taxonomic coverage in reference databases. Here, we present new primer sets designed to amplify fragments of the DNA barcoding region of the vertebrate COI gene, while avoiding co-amplification of mosquito templates, without multiplexed or nested PCR. Primers were validated using host vertebrate DNA templates from mosquito blood meals of known origin, representing all terrestrial vertebrate classes, and field-collected mosquito blood meals of unknown origin. We found that the primers were generally effective in amplifying vertebrate host, but not mosquito DNA templates. Applied to the sample of unknown mosquito blood meals, > 98% (60/61) of blood meals samples were reliably identified, demonstrating the feasibility of identifying mosquito hosts with the new primers. These primers are beneficial in that they can be used to amplify COI templates from a diverse range of vertebrate hosts using standard PCR, thereby streamlining the process of identifying the hosts of mosquitoes, and could be applied to next generation DNA sequencing and metabarcoding approaches.

Triatomines (Hemiptera, Reduviidae) blood intake: Physical constraints and biological adaptations

In order to efficiently obtain blood from their vertebrate hosts, bloodsucking arthropods have undergone an evolutionary selection process leading to specialist adaptations in their feeding apparatus (mouthparts and suction pumps) and salivary molecules. These adaptations act to counteract haemostasis, inflammation, and immune responses in their vertebrate hosts. The association of haematophagous arthropods with vertebrate hosts during a blood feed allows the transmission of pathogens between their hosts and vectors in a tripartite interaction. Feeding mechanisms in haematophagous arthropod species have been the subject of studies over at least eight decades worldwide, as a consequence of the importance of vector-borne diseases and their impact on human health. Here we review studies of the feeding mechanisms of triatomine bugs, with a particular focus on factors that influence their feeding performance when obtaining a blood meal from different vertebrate hosts.

Root Effect Haemoglobins in Fish May Greatly Enhance General Oxygen Delivery Relative to Other Vertebrates

The teleost fishes represent over half of all extant vertebrates; they occupy nearly every body of water and in doing so, occupy a diverse array of environmental conditions. We propose that their success is related to a unique oxygen (O₂) transport system involving their extremely pH-sensitive haemoglobin (Hb). A reduction in pH reduces both Hb-O₂ affinity (Bohr effect) and carrying capacity (Root effect). This, combined with a large arterial-venous pH change (ΔpH_a-v) relative to other vertebrates, may greatly enhance tissue oxygen delivery in teleosts (e.g., rainbow trout) during stress, beyond that in mammals (e.g., human). We generated oxygen equilibrium curves (OECs) at five different CO₂ tensions for rainbow trout and determined that, when Hb-O₂ saturation is 50% or greater, the change in oxygen partial pressure (ΔPO₂) associated with ΔpH_a-v can exceed that of the mammalian Bohr effect by at least 3-fold, but as much as 21-fold. Using known ΔpH_a-v and assuming a constant arterial-venous PO₂ difference (P_a-vO₂), Root effect Hbs can enhance O₂ release to the tissues by 73.5% in trout; whereas, the Bohr effect alone is responsible for enhancing O₂ release by only 1.3% in humans. Disequilibrium states are likely operational in teleosts in vivo, and therefore the ΔpH_a-v, and thus enhancement of O₂ delivery, could be even larger. Modeling with known P_a-vO₂ in fish during exercise and hypoxia indicates that O₂ release from the Hb and therefore potentially tissue O₂ delivery may double during exercise and triple during some levels of hypoxia. These characteristics may be central to performance of athletic fish species such as salmonids, but may indicate that general tissue oxygen delivery may have been the incipient function of Root effect Hbs in fish, a trait strongly associated with the adaptive radiation of teleosts.

The immunoglobulins of cold-blooded vertebrates

Although lymphocyte-like cells secreting somatically-recombining receptors have been identified in the jawless fishes (hagfish and lamprey), the cartilaginous fishes (sharks, skates, rays and chimaera) are the most phylogenetically distant group relative to mammals in which bona fide immunoglobulins (Igs) have been found. Studies of the antibodies and humoral immune responses of cartilaginous fishes and other cold-blooded vertebrates (bony fishes, amphibians and reptiles) are not only revealing information about the emergence and roles of the different Ig heavy and light chain isotypes, but also the evolution of specialised adaptive features such as isotype switching, somatic hypermutation and affinity maturation. It is becoming increasingly apparent that while the adaptive immune response in these vertebrate lineages arose a long time ago, it is most definitely not primitive and has evolved to become complex and sophisticated. This review will summarise what is currently known about the immunoglobulins of cold-blooded vertebrates and highlight the differences, and commonalities, between these and more “conventional” mammalian species.

[Comparative evaluation of morphofunctional organization of vertebrate nuclear blood cells]

Morphometrical parameters, osmoregulatory possibilities, and the membrane reserve value of nuclear hemocytes (leukocytes and erythrocytes) were studied in the main classes of vertebrates by using method of hypoosmotic loads. It has been established that in the fish--mammals line in erythrocytes the absolute reserve of the plasmalemma decreases and the relative area of the cell surface increases. Evolution of leukocytes is accompanied by an increase of the membrane reserve and of the surface area due to a decrease of volume and to a rise of folding of the plasmalemma.

Generation of monoclonal antibodies to vertebrate albumins for analysis of arthropod blood meals

An immunoassay using monoclonal antibodies (MAbs) that are specific for different vertebrate taxa (from class to species) has been developed that simplifies and facilitates analysis of vertebrate blood meals from arthropod vectors. The MAbs have been prepared against the single protein albumin, the most abundant protein in vertebrate sera. A panel of these antibodies has been generated against albumins from 33 species of vertebrates, representing four classes, 15 orders, and 25 families. Immunoreactivity of albumin in mosquito blood meals can be detected as late as 48 h after feeding. Immunoassays with MAbs can be carried out in the field as well as the laboratory. Used in conjunction with nucleic acid assays or used alone with an appropriate assortment of antibodies, the assay is simple, sensitive, and unambiguous.

Comparison of engorged Culex quinquefasciatus collection and blood-feeding pattern among four mosquito collection methods in Puerto Barrios, Guatemala, 2007

Investigators have used a variety of techniques to sample resting, engorged mosquitoes for the purposes of studying mosquito blood-feeding behavior. However, evidence exists that mosquito blood-feeding patterns may vary according to collection method. Engorged mosquitoes were collected from rural and urban habitats after the 2007 dry (July) and wet (December) seasons in the Department of Izabal, Guatemala, with the use of Centers for Disease Control and Prevention (CDC) light traps, gravid traps, and aspiration from plastic pots and vegetation. We evaluated the utility of plastic pots as sampling tools for engorged Culex mosquitoes and compared Cx. quinquefasciatus blood host identities among collection methods. The array of vertebrate hosts supplying blood to Cx. quinquefasciatus did not differ significantly by method of collection. The density of engorged Cx. quinquefasciatus per trap-night was not significantly different between CDC light traps, gravid traps, and plastic pots; however, there was a significantly higher proportion of total mosquitoes that were engorged collected from pots than from either CDC light traps or gravid traps.

Evolution of vertebrate haemoglobins: Histidine side chains, specific buffer value and Bohr effect

This review highlights the use of analytical tools, recently developed in the comparative method of evolutionary biology, for the study of haemoglobin (Hb) adaptation. It focuses on the functional consequences of a previously largely ignored structural feature of Hb, namely the degree and positional specificity of histidine (His) substitution in Hb chains. The importance of His side chains for hydrogen ion buffering, blood CO(2) transport capacity and the molecular mechanism of the Bohr effect in vertebrate Hbs is discussed. Using phylogenetically independent contrasts, a significant correlation between the specific buffer value of Hb and the number of predicted physiological buffer groups from Hb sequence data is shown. In a new result, the evolution of the number of physiological buffer groups in 77 vertebrate species is reconstructed on a phylogenetic tree. The analysis predicts that teleost fishes, passeriform birds and some snakes have independently evolved a much-reduced specific buffer value of Hb, possibly for enhancing the efficiency of an acid load to change oxygen affinity via the Bohr effect. This analysis demonstrates how in comparative physiology analysis of genetic databases in an evolutionary framework can identify candidate species for further experimental in vitro and whole animal studies.

Circulating serotonin in vertebrates

The role of circulating serotonin is unclear and whether or not serotonin is present in the blood of non-mammalian species is not known. This study provides the first evidence for the presence of serotonin in thrombocytes of birds and three reptilian species, the endothermic leatherback sea turtle, the green sea turtle and the partially endothermic American alligator. Thrombocytes from a fresh water turtle, American bullfrog, Yellowfin tuna, and Chinook salmon did not contain serotonin. Serotonin is a vasoactive substance that regulates skin blood flow, a major mechanism for endothermic body temperature regulation, which could explain why circulating serotonin is present in warm-blooded species. The temperature sensitivity of human blood platelets with concomitant changes in serotonin content further supports a link between circulating serotonin and thermoregulation. Phylogenetic comparison of the presence of circulating serotonin indicated an evolutionary divergence within reptilian species that might coincide with the emergence of endothermy.

Comparative physiology and molecular evolution of carbonic anhydrase in the erythrocytes of early vertebrates

The different isozymes of carbonic anhydrase (CA) have been the subject of intensive study in mammals, but there is still much to be learned about the early evolution of this enzyme in vertebrates. Erythrocyte CA plays an essential role in the respiratory processes of most vertebrates and is probably the most well studied CA isozyme. The available evidence indicates that there has been a progressive increase in the efficiency of erythrocyte CA during the early evolution of vertebrates. There also appears to be a substantial increase in erythrocyte CA activity during development in some species. At the present time, however, the selective pressures that may be influencing the properties of erythrocyte CA during vertebrate evolution and development have not been clearly determined. When the available molecular sequence information is examined, it is evident that the erythrocyte CAs of early vertebrates have active sites that are more similar to those of mammalian CA VII and II, rather than CA I. We can now also begin to examine the phylogenetic relationships between the different rbc CAs in vertebrates, but more CA sequence information is clearly required from different groups of vertebrates before we have a complete picture of the molecular evolution of erythrocyte CA.

Molecular evolution of the vertebrate blood coagulation network

In mammalian blood coagulation 5 proteases, factor VII (FVII), factor IX (FIX), factor X (FX), protein C (PC) and prothrombin act with two cofactors factor V and factor VIII to control the generation of fibrin. Biochemical evidence and molecular cloning data have previously indicated that blood coagulation involving tissue factor, prothrombin and fibrinogen is present in all vertebrates. Using degenerate RT-PCR we have isolated and characterized novel cDNAs with sequence identity to the blood coagulation serine proteases and cofactors from chicken and the puffer fish (Fugu rubripes). Sequence alignments, phylogenetic and comparative sequence analysis all support the existence of the Gla-EGF1-EGF2-SP domain serine proteases FVII, FIX, FX, PC and the A1-A2-B-A3-C1-C2 domain protein cofactors FV and FVIII in these species. These results strongly suggest that the blood coagulation network is present in all jawed vertebrates and evolved before the divergence of tetrapods and teleosts over 430 million years ago; and that vertebrate blood coagulation may have benefited from two rounds of gene or whole genome duplication. Sequences identified in Fugu coding for additional FVII-like, FIX-like and PC-like sequences support the possibility of further tandem and large-scale duplications in teleosts. Comparative sequence analyses of amino acid residues in the active site region suggest these additional sequences have evolved new and as yet unknown functions.

Role of arthropod saliva in blood feeding: sialome and post-sialome perspectives

This review addresses the problems insects and ticks face to feed on blood and the solutions these invertebrates engender to overcome these obstacles, including a sophisticated salivary cocktail of potent pharmacologic compounds. Recent advances in transcriptome and proteome research allow an unprecedented insight into the complexity of these compounds, indicating that their molecular diversity as well as the diversity of their targets is still larger than previously thought.

The bigger the C-value, the larger the cell: genome size and red blood cell size in vertebrates

Vertebrate genome sizes vary roughly 350-fold and correlate with a variety of cellular and organismal parameters. Most notable among these is the relationship between genome size ("C-value") and red blood cell (RBC) size, which can be identified within and among each of the five vertebrate classes. This relationship, in turn, leads to important associations between genome size and features such as metabolic rate (at least in homeotherms). The present article describes the correlation between genome size and RBC size in vertebrates and discusses some of the cytological, physiological, and evolutionary implications of this relationship.

Leishmania immune adherence reaction in vertebrates

In normal human blood, C3-opsonized Leishmania promastigotes immune adhere to erythrocytes, a mechanism believed to enhance their clearance from blood and phagocytosis. Given the potential importance of this reaction in host defence against infection, the promastigote-erythrocyte interaction was studied in blood of individuals from one avian and 12 mammalian genera; [111In]-labelled promastigotes were found to bind only to primate erythrocytes. Nevertheless, previous experiments coincubating platelets isolated from nonprimate mammals with C3-opsonized promastigotes led to promastigote-platelet adherence. To ascertain whether this is a natural mechanism in nonprimate Leishmania infection, normal blood from members of Leishmania animal models of interest, dog, guinea-pig, hamster, mouse and rabbit, was infected ex vivo with promastigotes. Within 1 min of blood contact, the promastigote surface was loaded with platelets, rapidly evolving into large aggregates. These results confirm the physiological nature of the reaction and demonstrate that promastigote-erythrocyte and promastigote-platelet binding are the first parasite-host cell encounters after Leishmania invasion of primates and nonprimate mammals, respectively. Leishmania immune adherence shares the characteristics of the nonanticipatory immune systems, and we consider it should be viewed as an innate vertebrate host effector mechanism.

Tetranectin-like protein in vertebrate serum: a comparative immunochemical analysis

The glycoprotein tetranectin (TN) found in human serum is a 90-kDa homotrimeric C-type lectin binding Ca2+, heparin and plasminogen kringle 4. TN is suggested as being implicated in tissue remodelling. The antigenic reactivity of putative TN was examined in serum from 14 different animal species using three sandwich enzyme immunoassays for human TN. Crab-eating macaque serum showed the strongest reaction, followed by horse and cat. Serum from cow, goat, pig, mouse and chicken reacted weakly, while dog, trout, and the amphibian and the reptile species did not react. The TN-like protein from macaque, horse and cat serum bound heparin and showed the same dependence on Ca2+ for interaction with the monoclonal antibodies as human TN. Gel filtration of sera from the three animal species showed that the TN-like protein eluted as single peaks with a M(r) of 70-90 kDa. Western blotting of horse and cat TN-like protein electrophoresed under reducing conditions showed that the antibodies against human TN reacted with a single band with an approximate M(r) of 30 kDa, indicating that the TN-like protein is also a homotrimer. Horse and cat TN-like protein interacted with human kringle 4-sepharose. Most likely, the reacting protein represents crab-eating macaque, horse and cat homologues of human TN.

Components of normal serum block the focal segmental glomerulosclerosis factor activity in vitro

BACKGROUND

Sera from some patients with focal segmental glomerulosclerosis (FSGS) increase glomerular albumin permeability (P(alb)) in vitro. The hypothesis that a component of normal serum can protect the glomerular permeability barrier was tested using sera from FSGS patients, normal individuals, and several mammalian and avian species.

METHODS

In most experiments, isolated rat glomeruli were incubated in medium containing FSGS serum known to increase P(alb) in vitro, normal serum, or both active FSGS and normal serum. In other experiments, fractions of normal serum and serum from other vertebrate species were incubated with active FSGS serum. P(alb) was calculated from glomerular capillary expansion in response to an oncotic gradient. To enrich the blocking activity, normal pooled human plasma was subjected to various biochemical manipulations.

RESULTS

Normal human serum prevented the increase in P(alb) (active FSGS sera, 0.77 +/- 0.12; active FSGS sera:normal serum, 1:1 mix, 0.06 +/- 0.30, P < 0.001). Protection diminished as the concentration of normal serum was decreased. Specific fractions of human serum, including human albumin and immunoglobulin fractions, were not protective. Blocking activity was present in 80% ammonium sulfate precipitate and certain fractions from size-exclusion chromatography of normal pooled human plasma. Normal serum from each of the vertebrate species tested also prevented the increase in P(alb). Preincubation with normal serum was protective during subsequent incubation with FSGS serum, but normal serum was not protective after preincubation with FSGS serum.

CONCLUSIONS

We conclude that a factor or factors in normal serum block the permeability effect of active FSGS sera. This phenomenon may account for variability in proteinuria among patients with FSGS and may explain inconsistent proteinuria following injection of FSGS sera into experimental animals. Characterization of the protective substance(s) and the mechanism by which the increase in permeability is blocked may provide insight into the pathogenesis of FSGS.

Phospholipid and cholesteryl ester transfer activities in plasma from 14 vertebrate species. Relation to atherogenesis susceptibility

Cholesteryl ester and phospholipid transfer activities were determined in plasmas from 14 vertebrates, and lipid transfer values were analyzed in the light of the known atherogenesis susceptibility of studied species. Whereas cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) activities among vertebrate species were only measured in lipoprotein-deficient fractions in previous studies, both endogenous lipoprotein-dependent and endogenous lipoprotein-independent assays were used in the present work. In agreement with previous studies, a few species (chicken, man, rabbit and trout) displayed substantial CETP activity, whereas CETP activity was not detectable in other species (cow, dog, horse, mouse, pig, and rat). Additional species that were not studied before, i.e. cat, goat, and sheep, were shown to be deficient in plasma cholesteryl ester transfer activity, while duck was shown to constitute a new member of the high activity group. Unlike CETP activity, PLTP activity was detected in plasmas from all studied species, most of them being assayed here for the first time (cat, chicken, cow, duck, goat, horse, sheep, and trout). While dog, trout, mouse, and pig displayed the highest phospholipid transfer activity levels, the remarkable preservation of facilitated phospholipid transfers in plasma from all vertebrates might indicate an essential role of PLTP in vivo. Interestingly, animals with well-documented atherogenesis susceptibility (chicken, pig, rabbit, and man) displayed significantly higher mean CETP activity, but lower mean PLTP activity than known 'resistant' animals (cat, dog, mouse, and rat). In conclusion, the present study revealed marked differences in plasma lipid transfer activities between vertebrate species, and interspecies comparisons indicated that both CETP and PLTP may constitute two determinants of the atherogenicity of the plasma lipoprotein profile.

Hyperglycemia in hummingbirds and its consequences for hemoglobin glycation

We measured levels of glucose and glycated hemoglobin in the blood of three of the world's smallest nectarivorous birds, the Anna's (Calypte anna), Costa's (Calypte costae), and ruby-throated hummingbirds (Archilochus colubris). Plasma glucose levels of hummingbirds that were fasted overnight (17 mM) were higher than those in any mammal and are among the highest ever measured in a fasting vertebrate. Glucose levels in hummingbirds just after feeding were extreme, rising as high as 42 mM. The surprisingly high blood glucose concentrations in hummingbirds were accompanied by glycated hemoglobin levels that are the highest ever measured in birds but are lower than those of non-diabetic humans. How hummingbirds tolerate blood glucose levels that cause serious neurological and microvascular pathologies in diabetic humans and animals remains unknown.

Volume-sensitive transport systems and volume homeostasis in vertebrate red blood cells

Animal cells regulate their volume in the short term by controlling solute movements into and out of the cell. A quite of dissipative transport systems are involved which allow either regulatory volume increase (RVI) or decrease (RVD) responses depending upon the direction of the electrochemical gradients of the solutes. Many of these transporters have been identified at the molecular level and structure-function studies have identified transmembrane transport domains and cytoplasmic regulatory domains. In vertebrate red blood cells, protein phosphorylation appears to be central to the coordinated regulation of transporter activity. Inhibitors of protein phosphatases (PPs) cause inhibition of the K+/Cl- cotransporter (a transporter mediating RVD), whilst some inhibitors of protein kinases (PKs) cause activation. A sequence of potential phosphorylation sites appears to constitute a cascade of reactions leading to transporter regulation. PP and PK inhibitors have opposite effects on transporters mediating RVI responses, which is consistent with the coordinated but reciprocal regulation of transporters activated during both RVI and RVD using some common phosphorylation reactions. The transporters are sensitive to other stimuli including, in red blood cells, changes in PO2 and pH. These responses are also sensitive to PK/PP inhibitors and may involve elements of the volume-sensitive transduction pathway.

Oxygen and carbon dioxide transport in vertebrate erythrocytes: an evolutionary change in the role of membrane transport

Two major strategies are apparent for the regulation of gas transport by vertebrate blood except in the myxinoids, which seem to have little scope for such regulation. In lampreys and teleost fish, haemoglobins have low buffering capacities and large Bohr/Haldane effects. Na+/H+ exchange plays an important role in the control of haemoglobin oxygen-affinity in these vertebrate groups. The large Bohr/Haldane effect also facilitates carbon dioxide transport: the blood (or erythrocyte) pH increases upon deoxygenation, thus increasing the concentration of bicarbonate formed at a given carbon dioxide tension. In lampreys, the bicarbonate permeability of the erythrocyte membrane is low. As a consequence, extracellular acid loads cannot be buffered by haemoglobin. In contrast, teleost erythrocytes possess a functional anion exchange, allowing extracellular proton loads to be buffered by haemoglobin. However, because the buffering capacity of teleost haemoglobins is low, buffering of extracellular acid loads is less effective in teleost fish than in elasmobranch fish and in air-breathing vertebrates whose haemoglobins have a high buffering capacity. However, the high buffering capacity of the haemoglobins diminishes the possibility of regulating haemoglobin oxygen-affinity via secondarily active Na+/H+ exchange, because intracellular pH changes, caused by proton efflux, remain small.

[Various physico-chemical properties of hemoglobins in representatives of different classes of vertebrates]

The level of hydrophobic property and microviscosity in central and peripheral sections of molecules of main electrophoretic fractions of hemoglobins in representatives of different classes of vertebrates has been studied by means of the methods of fluorescent spectroscopy. It has been found that central sections of hemoglobin molecules are characterized by less pronounced changes in the volume and level of hydrophobic properties and highly pronounced changes in the packing integrity as compared to peripheral sections of the protein globule. Peripheral sections of hemoglobin molecules in the mammals are characterized by higher amount of surface tyrosines and lower level of hydrophobic properties against similar indices in representatives of other classes of vertebrates. Microviscosity (packing compaction) in central sections of hemoglobin molecules decreases with a transfer from low phylogenetic groups of vertebrates to higher ones.

Developmental biology of hematopoiesis

The cellular and environmental regulation of hematopoiesis has been generally conserved throughout vertebrate evolution, although subtle species differences exist. The factors that regulate hematopoietic stem cell homeostasis may closely resemble the inducers of embryonic patterning, rather than the factors that stimulate hematopoietic cell proliferation and differentiation. Comparative study of embryonic hematopoiesis in lower vertebrates can generate testable hypotheses that similar mechanisms occur during hematopoiesis in higher species.

[The species characteristics of the intramolecular structure of hemoglobin in vertebrates]

Using fluorescence spectroscopy species peculiarity of hydrophobic and microviscosity degree in central and peripheral molecular areas of the main electrophoretic haemoglobin fractions in representatives of different vertebrate classes gas been studied. It is established that central areas of haemoglobin molecule are characterised by twice lesser variability of size and hydrophobic degree and 2.4 times greater variability of package strength as compared with peripheral areas of protein globule.

[The interaction of organosilicon bisammonium compounds with the cholinesterases of Far-Eastern squids and vertebrates. The comparative enzymological, kinetic and conformational aspects]

The research of interaction of cholinesterases from human erythrocytes, horse blood serum, brain of the frog Rana temporaria, optical ganglia of the Pacific squid Todarodes pacificus, as well as optical ganglia of specimens of the Comandor squid Berryteuthis magister from different areas in the Bering sea with 13 organosilicon bis (trimethylammonium) compounds (silane and siloxane rows) as reversible cholinesterase inhibitors have been first studied and generalized. Calculations of the effector structure using the method of theoretical conformational analysis showed higher rigidity of interonium chain of siloxane derivatives and gave grounds to accept the asymmetry of hydrate envelope for these compounds. The data of conformational and kinetic analysis allowed to propose that specificity of antienzymic effect of organosilicon compounds was mainly due to conformational flexibility of interonium chain and the nature of hydration of effector molecule. The new information on the mechanism of catalytic reactions effected by cholinesterases from animals at different evolutionary stages was obtained.

[The comparative characteristics of the physicochemical and structural-functional properties of hemoglobin in a number of vertebrates]

Using isoelectrofocusing within pH gradient 6-8, studies have been made on microheterogeneity of haemoglobins from various vertebrates. Phylogenetic evaluation of oxygen affinity of the main and minor electrophoretically pure haemoglobin fractions is given. It was shown that oxygen affinity of the haemoglobins is related to the ratio between dicarboxylic and basic amino acids.

Evolution of marsupial and other vertebrate thyroxine-binding plasma proteins

Binding of radioactive thyroxine to proteins in the plasma of vertebrates was studied by electrophoresis followed by autoradiography. Albumin was found to be a thyroxine carrier in the blood of all studied fish, amphibians, reptiles, monotremes, marsupials, eutherians (placental mammals), and birds. Thyroxine binding to transthyretin was detected in the blood of eutherians, diprotodont marsupials, and birds, but not in blood from fish, toads, reptiles, monotremes, and Australian polyprotodont marsupials. Globulins binding thyroxine were only observed in the plasma of some mammals. Apparently, albumin is the phylogenetically oldest thyroxine carrier in vertebrate blood. Transthyretin gene expression in the liver developed in parallel, and independently, in the evolutionary lineages leading to eutherians, to diprotodont marsupials, and to birds. In contrast, high transthyretin mRNA levels, strong synthesis, and secretion of transthyretin in choroid plexus from reptiles and birds indicate that transthyretin gene expression in the choroid plexus evolved much earlier than in the liver, probably at the stage of the stem reptiles. NH2-terminal sequence analysis suggests a change of transthyretin pre-mRNA splicing during evolution.

The isolation and partial characterization of alpha 2-macroglobulin from the serum of the ostrich (Struthio camelus

1. alpha 2-Macroglobulin (alpha 2M) activity is present in the serum of the ostrich, Struthio camelus. The chromogenic synthetic peptide substrates BAPNA and ATNA were hydrolysed by trypsin and chymotrypsin, respectively, in the presence of ostrich serum and the alpha 2 M in ostrich serum protected trypsin from being inhibited by soybean trypsin inhibitor. Ostrich alpha 2M proved to be a potent inhibitor of bovine pancreatic trypsin and chymotrypsin. 2. alpha 2M was purified to apparent homogeneity by PEG precipitation, DEAE-Toyopearl 650M, Bio-Gel A-5m and Zn(2+)-affinity chromatography. 3. Ostrich alpha 2M migrated as a single band (M(r) 779,000 during non-denaturing gradient gel electrophoresis and showed increased mobility after reaction with trypsin. Denaturation dissociated ostrich alpha 2M into half-molecules. Denaturation with reduction further dissociated the protein into quarter-subunits. 4. Isoelectric focusing revealed a pI of 5.3. 5. The amino acid composition of ostrich alpha 2M is typical of an alpha 2M, comparing favourably with those of other animal species. The carbohydrate composition of the purified protein, in percentage dry weight of the molecule, was galactose: mannose (1:1), 4.55; N-acetylglucosamine 2.35; N-acetylneuraminic acid, 0.58; and fucose, 0.77. 6. alpha 2M was assessed immunologically by Ouchterlony double-diffusion and Western blot analysis with polyvalent antisera directed against ostrich alpha 2M. 7. Ostrich alpha 2M seems to show many physical, chemical and kinetic properties similar to those of other known alpha 2M(s), but is expected to differ from other alpha Ms when considering the primary structure of the bait region, the area differing among alpha Ms from different species and determining its specificity.

ACTH-like molecules in lymphocytes. A study in different vertebrate classes

Immunocytochemical and cytofluorimetric studies were performed in several species of different classes (Pisces, Amphibia, Reptilia and Aves), in order to ascertain the presence of ACTH-like molecules in blood cells. Using monoclonal and polyclonal antibodies, we demonstrated that lymphocytes containing ACTH-like molecules are first detectable in anuran amphibia, and are present in lymphocytes of reptilia and aves. Taking into account previous results demonstrating that ACTH-like molecules are present in and modulate macrophage functions from molluscs to man, it is argued that a new biological role has probably been acquired by ACTH in higher vertebrates, where it is also expressed in cells belonging to the lymphocyte lineage, possibly exerting a regulatory role on antibody response.

Isolation and properties of a fatty acid-binding protein from the Pacific lamprey (Lampetra tridentata)

1. A survey of 12 vertebrate species showed that palmitate was bound by an albumin-like serum protein in all classes tested except the dogfish and the lamprey. 2. The major palmitate-binding protein of the Pacific lamprey was isolated and found to be of molecular mass 19,000. 3. The amino acid composition of this protein indicates that it is not a member of the albumin superfamily. 4. The 19-kDa lamprey protein binds bilirubin, cortisol and tryptophan only weakly, but binds palmitate with KA = 25 microM-1, comparable to the first long-chain fatty acid site of bovine albumin (KA = 34 microM-1).

Discrimination between adaptive and neutral amino acid substitutions in vertebrate hemoglobins

A discriminant analysis on the basis of the physicochemical properties of amino acid residues is developed to investigate the accumulation pattern of amino acid substitutions in a family of proteins. The application of this analysis to vertebrate hemoglobins reveals the following new results. (1) The major components of teleost fish and amphibian hemoglobins showing the Root effect are sharply discriminated from mammalian hemoglobins in several regions of the alpha and beta chains, whereas shark, minor components of teleost fish and amphibian, reptile, and bird hemoglobins showing no Root effect exhibit a gradual change to mammalian hemoglobin in a straightforward way. This result suggests at least two lines of molecular evolution in vertebrate hemoglobins. (2) The nonadult hemoglobin chains are allocated to the latter line, i.e., tadpole, zeta, and pi chains are similar to shark and trout I chains, and epsilon and gamma chains are similar to some of the reptile chains. (3) In any case, most of the amino acid residues causing the discrimination are located near the sites that carry the amino acid residues conserved well throughout all classes of vertebrates, suggesting that modifications adapting to the respective living conditions or respiratory organs have taken place effectively near the amino acid residues essential for the manifestation of cooperative oxygen binding. (4) The amino acid residues at other sites are changed from one to another species even within the same class, showing a constant substitution rate as a whole. These amino acid substitutions may be nearly neutral, being under a weak functional constraint. The number of sites allowing such neutral substitutions is rather small, less than one-half of all the sites in the adult hemoglobins of bird and mammal, whereas it amounts to two-thirds in teleost fish hemoglobins.

Aldehyde dehydrogenase activity in blood from various vertebrates

1. Aldehyde dehydrogenase activity was determined in whole blood samples from 17 selected vertebrates of 5 classes, using 3,4-dihydroxyphenylacetaldehyde (the aldehyde derived from dopamine) as substrate. 2. Aldehyde dehydrogenase activity in blood was widely but unevenly distributed among the species studied. 3. Mean aldehyde dehydrogenase activities in the range of 40-140 nmol/min.ml blood (measured at 37 degrees C, pH 8.8) were found in blood from man, monkey, rabbit, guinea pig and mouse (C57BL and NMRI strains), with the highest activity in rabbit blood. 4. Much lower aldehyde dehydrogenase activities (0.5-7.5 nmol/min.ml blood) were found in blood from Sprague-Dawley and Wistar rat, dog, cat, horse, pig, chicken, caiman, frog and rainbow trout, whereas the activities in blood from DBA mouse, cow, sheep and crucian carp were close to the detection limit.

Plasma calcium difference between man and vertebrates

1. Literature data about the plasma content of total calcium, ionized calcium and inorganic phosphate in healthy animals and man of different age and sex were collected. 2. It was established that under normal conditions ionized calcium is about 45% of total calcium. 3. The degree of saturation of these blood samples with respect to octocalcium phosphate OCP was calculated. 4. In young animals and man the blood plasma has a higher degree of saturation than in adult animals and man. 5. The blood plasma of healthy animals is supersaturated with respect to OCP during their whole life. 6. However, the blood plasma of healthy human adults is slightly undersaturated with respect to OCP.

Degree of saturation of blood plasma in vertebrates with octocalcium phosphate

In previous papers it has been shown that octocalcium phospate OCP occurs in bone mineral of vertebrates. Although this compound is not stable, there is a continuous new-formation of OCP due to bone turnover. Literature data of the calcium and phosphate concentrations in the blood plasma of vertebrates were collected and the degree of saturation with OCP was calculated. The results show that blood plasma of vertebrates is almost saturated with OCP. This fact indicates that OCP is the solubility controlling phase in the mineral of vertebrates. Further it verifies the expectation based on physicochemical theory that the interaction between body fluids and bone mineral is important in the calcium and phosphate homeostasis.

Iron-binding properties and amino acid composition of marsupial transferrins: comparison with eutherian mammals and other vertebrates

1. Some physicochemical properties of transferrin from three marsupials, viz a possum (Trachosurus vulpecula), a kangaroo (Macropus fuliginosus) and the quokka (Setonix brachyurus) were studied and compared with those of transferrins from mammalian and non-mammalian vertebrate species. 2. The molecular weight of the marsupial transferrins fell within the range of 76,000-79,000 daltons. 3. The marsupial transferrins were similar to the transferrins of eutherian mammals with respect to optical spectral properties, iron binding capacity and the pH-dependence of iron binding, and iron release mediated by 2,3-DPG. 4. The amino acid compositions of the marsupial transferrins were compared with each other and with the transferrins from the other vertebrate species. The compositions of the marsupial transferrin were closely related to each other, and also showed similarities with transferrins from eutherian mammals and chicken ovotransferrin.

Endogenous cardiac glycosidelike compounds

The possibility that endogenous inhibitors of the sodium pump exist and bind to the cardiac glycoside binding site on Na+,K+-adenosine triphosphatase (ATPase) has been a source of much controversy. Although numerous hormones and inorganic ions that modulate Na+,K+-ATPase activity have been described, most of these affect the sodium pump indirectly by varying the intracellular sodium concentration or by increasing the number of enzyme units. None of these endogenous compounds has been shown conclusively to modulate sodium pump activity by binding to the cardiac glycoside binding site on Na+,K+-ATPase. However, the near-universal presence of three high-affinity binding sites on the alpha-subunit of the enzyme has engendered much speculation that endogenous ligands for these receptors must exist. In addition, none of the hormones known to indirectly affect sodium pump activity in vivo has been shown to modulate Na+,K+-ATPase activity in response to extracellular volume expansion or to play a role in the pathogenesis of hypertension or chronic renal failure, conditions in which a circulating inhibitor of Na+,K+-ATPase has been implicated. This report presents a condensed history of the search for endogenous inhibitors of Na+,K+-ATPase and describes recent advances in the field. Despite progress in identifying and characterizing compounds that could affect Na+,K+-ATPase activity in vivo, definitive proof for the existence of endogenous ligands for the cardiac glycoside binding site remains elusive.

Ubiquitous presence of calciferin-like and cathepsin D-like activities in the sera (vertebrates) and humoral fluids (invertebrates)

1. Sera (or humoral fluids) from various animals (vertebrates and invertebrates) were assayed for calciferin-like and cathepsin D-like activities, indicating the ubiquitous presence of the latter and the former (with a few exceptions). Animals other than the mammals appeared to contain an organophilic calciferin-like activity in addition to a hydrophilic component (calciferin). 2. A correlation was found between the levels of calciferin and acid protease in most of the mammalian sera. An age-dependent decrease in calciferin (but not acid protease) was found in human sera. The possible presence of an acid protease-inhibitor was suggested.

Sheep haemopexin: immunological cross-reactivity with other vertebrate sera and evidence for the absence of haemopexin in some mouflon

A monospecific antiserum to sheep haemopexin was produced in rabbits. By using this antiserum, as well as absorbed antisera to sheep and mouflon serum proteins, it was proved that some mouflon sera lack haemopexin. In immunodiffusion, when using the monospecific antiserum, immunoprecipitates were present only in species' belonging to suborder Ruminantia. None of the other mammalian, nor any of the avian, reptilian, amphibian and fish species tested, showed reaction.

Anadara ovalis hemoglobins: distinct dissociation and ligand binding characteristics

The red cells of the arcid clam Anadara ovalis contain two electrophoretically distinct hemoglobins: Hb Major (Hb Ma) and Hb Minor (Hb Mi). The major component consists of two electrophoretically indistinguishable tetramers each composed of two heterodimers; the minor hemoblogin is a homodimer whose subunits are different from the tetramer. Functionally, Hb Ma has a higher P50, exhibits a concentration dependent oxygen affinity, has significant ligand cooperativity (n = 2.0), lacks a Bohr effect and is unaffected by ATP. HB Mi has a P50 which is lower and independent of hemoglobin concentration, shows appreciable cooperativity (n = 1.4) and exhibits no heterotropic effects. Both Hb Ma and Mi are resistant to dissociation in the presence of 1.0 M NaI, NaCl and guanidine-HCl but dissociate to monomers when converted to the aquamet but not the cyanmet derivative. The dissociation is completely inhibited by mercaptoethanol. The large number of reactive -SH groups (10-13 per tetramer) suggests that the monomerization is mediated by intra-subunit disulfide bridge formation.