A SAMPLE SURVEY OF SELECTED AREAS IN AND NEAR LITTLE ROCK, ARKANSAS, TO ASSESS THE PREVALENCE OF ENTAMOEBA HISTOLYTICA. (25/247)

Laboratory confirmed clinical amoebiasis was diagnosed among more than 50 persons by the University of Arkansas Medical Center from 1965 to 1961. The presence of this number of patients prompted an investigation into the prevalence of Entamoeba histolytica in four selected areas in and around Little Rock, Arkansas. The results of the study, using a sample survey technique, showed that it is possible to have a seemingly large number of clinically significant cases of amoebiasis in a population without a high prevalence of the parasite. Evidence was also obtained of the beneficial effects of improvements in sanitary facilities, as reflected in the lower amoebic prevalence rate in a 0-4-year age-group from one of the four areas surveyed in which a piped, indoor city-water supply and sewage facilities had been installed six years previously.  (+info)

EVOLUTION OF THE IMMUNE RESPONSE. I. THE PHYLOGENETIC DEVELOPMENT OF ADAPTIVE IMMUNOLOGIC RESPONSIVENESS IN VERTEBRATES. (26/247)

1. The California hagfish, Eptatretus stoutii, seems to be completely lacking in adaptive immunity: it forms no detectable circulating antibody despite intensive stimulation with a range of antigens; it does not show reactivity to old tuberculin following sensitization with BCG; and gives no evidence of homograft immunity. 2. Studies on the sea lamprey, Petromyzon marinus, have been limited to the response to bacteriophage T(2) and hemocyanin in small groups of spawning animals. They suggest that the lamprey may have a low degree of immunologic reactivity. 3. One holostean, the bowfin (Amia calva) and the guitarfish (Rhinobatos productus), an elasmobranch, showed a low level of primary response to phage and hemocyanin. The response is slow and antibody levels low. Both the bowfin and the guitarfish showed a vigorous secondary response to phage, but neither showed much enhancement of reactivity to hemocyanin in the secondary response. The bowfin formed precipitating antibody to hemocyanin, but the guitarfish did not. Both hemagglutinating and precipitating antibody to hemocyanin were also observed in the primary response of the black bass. 4. The bowfin was successfully sensitized to Ascaris antigen, and lesions of the delayed type developed after challenge at varying intervals following sensitization. 5. The horned shark (Heterodontus franciscii) regularly cleared hemocyanin from the circulation after both primary and secondary antigenic stimulation, and regularly formed hemagglutinating antibody, but not precipitating antibody, after both primary and secondary stimulation with this antigen. These animals regularly cleared bacteriophage from the circulation after both the primary and secondary stimulation with bacteriophage T(2). Significant but small amounts of antibody were produced in a few animals in the primary response, and larger amounts in the responding animals after secondary antigenic stimulation. 6. Studies by starch gel and immunoelectrophoresis show that the hagfish has no bands with mobilities of mammalian gamma globulins; that the lamprey has a single, relatively faint band of this type; and that multiple gamma bands are characteristic of the holostean, elasmobranchs, and teleosts studied. By this method of study, the bowfin appeared to have substantial amounts of gamma(2) globulin. 7. We conclude that adaptive immunity and its cellular and humoral correlates developed in the lowest vertebrates, and that a rising level of immunologic reactivity and an increasingly differentiated and complex immunologic mechanism are observed going up the phylogenetic scale from the hagfish, to the lamprey, to the elasmobranchs, to the holosteans, and finally the teleosts.  (+info)

MECHANISM OF THE PARALYSING ACTION OF PIPERAZINE ON ASCARIS MUSCLE. (27/247)

The effects of piperazine on Ascaris muscle cells have been investigated with electrophysiological techniques. These cells have an average resting potential of about 30 mV interrupted by rhythmic spikes of myogenic origin (1 to 7 spikes/sec). With piperazine (10(-3), w/v), the average resting potential increases above 40 mV and the pacemaker activity is suppressed. These changes are similar to those temporarily produced in the same cells by the electrical stimulation of inhibitory nerve fibres. Electrophoretic application of piperazine to different areas of the muscle cells shows that this drug hyperpolarizes their membrane only when applied to the region where both excitatory and inhibitory neuromuscular synapses are located. The degree of muscle hyperpolarization induced by piperazine depends upon the extracellular chloride concentration, decreasing when a fraction of the chloride ions is replaced by the larger, supposedly nonpenetrating, sulphate anions. Piperazine may, therefore, be regarded as a pharmacological analogue of a natural inhibitory transmitter.  (+info)

INFLUENCE OF SOME IONS ON THE MEMBRANE POTENTIAL OF ASCARIS MUSCLE. (28/247)

The influence of several ions on the membrane potential of the somatic muscle of Ascaris has been investigated by changing their concentration in the surrounding solution. When [K](o) is increased at the expense of [Na](o) leaving [Cl](o) constant, the membrane potential is first seen to increase. [K](o) higher than 45 mM reduces the membrane potential with a slope of 23 mv for a tenfold change in [K](o). However, when [K](o) is increased keeping [Na](o) and [Cl](o) low and constant, the line relating the membrane potential with log [K](o) has a slope of almost 50 mv. If [Cl](o) is reduced in the absence of external Na, after the [K](o) is increased to 45 mM, the membrane potential decreases with a slope of 59 mv per tenfold change in [Cl](o) in close agreement with the Nernst equation. If Cl(-) is replaced by SO(4) (2-), a depolarization is produced, while chloride replacement by NO(3) (-), Br(-), and I(-) results in a hyperpolarization of the membrane. Removal of the external Na(+) ions increases the average membrane potential by 17 mv.  (+info)

Dissection of the Ascaris sperm motility machinery identifies key proteins involved in major sperm protein-based amoeboid locomotion. (29/247)

Although Ascaris sperm motility closely resembles that seen in many other types of crawling cells, the lamellipodial dynamics that drive movement result from modulation of a cytoskeleton based on the major sperm protein (MSP) rather than actin. The dynamics of the Ascaris sperm cytoskeleton can be studied in a cell-free in vitro system based on the movement of plasma membrane vesicles by fibers constructed from bundles of MSP filaments. In addition to ATP, MSP, and a plasma membrane protein, reconstitution of MSP motility in this cell-free extract requires cytosolic proteins that orchestrate the site-specific assembly and bundling of MSP filaments that generates locomotion. Here, we identify a fraction of cytosol that is comprised of a small number of proteins but contains all of the soluble components required to assemble fibers. We have purified two of these proteins, designated MSP fiber proteins (MFPs) 1 and 2 and demonstrated by immunolabeling that both are located in the MSP cytoskeleton in cells and in fibers. These proteins had reciprocal effects on fiber assembly in vitro: MFP1 decreased the rate of fiber growth, whereas MFP2 increased the growth rate.  (+info)

Ascaris hemoglobin gene: plant-like structure reflects the ancestral globin gene. (30/247)

Animal globin genes have two introns at strictly conserved positions, while plant globin genes have both of these as well as an additional, central intron. It has been proposed that a common ancestor gene had three introns, one of which was subsequently lost from animal but not plant globin genes. We have elucidated the cDNA sequence and gene structure of a hemoglobin from the parasitic nematode Ascaris suum and found a plant-like central intron, providing strong evidence for a three-intron ancestor of modern globin genes.  (+info)

Distal heme pocket conformers of carbonmonoxy derivatives of Ascaris hemoglobin: evidence of conformational trapping in porous sol-gel matrices. (31/247)

We report the ligand dependence of the conformer distribution in the distal heme pocket of Ascaris suum hemoglobin (Hb) studied by resonance Raman spectroscopy. The heme-bound CO is used as a spectroscopic antenna to probe the original distribution of conformers in the dioxygen derivative of Ascaris Hb, by utilizing sol-gel encapsulation. The first step is to encapsulate the dioxygen derivative in the porous sol-gel and let the gel age, thus trapping the equilibrium conformational distribution of Ascaris dioxygen Hb. In the second step, the dioxygen ligand is replaced by CO. The sol-gel environment impedes any large scale movements, drastically slowing down the conformational relaxation triggered by the ligation change, essentially "locking in" the initial quaternary and even tertiary structure of the protein. Studying the Fe-CO frequencies of the latter sample allows evaluation of the distribution of the distal heme pocket conformers that was originally associated with the dioxygen derivative. Extending the study to the Ascaris mutants allows for examination of the effect of specific residues in the distal pocket on the conformational distribution. The choice of mutants was largely based on the anticipated variation in hydrogen bonding patterns. The results show that the sol-gel encapsulation can slow or prevent re-equilibration within the distal heme pocket of Ascaris Hb and that the distribution of distal heme pocket conformers for the CO derivative of Ascaris Hb in the sol-gel is highly dependent on the history of the sample. Additionally, we report a detailed study of the CO complex of the mutants in solution for assignment of the various heme pocket conformers, and we present a comparison of the sol-gel data with solution data. The results support a picture in which the dioxygen derivative biases the population strongly toward a tightly packed configuration that favors the network of strong hydrogen bonding interactions, and suggest that Ascaris Hb is uniquely designed for dioxygen capture.  (+info)

Structure and macromolecular assembly of two isoforms of the major sperm protein (MSP) from the amoeboid sperm of the nematode, Ascaris suum. (32/247)

Ascaris sperm are amoeboid cells that crawl by extending pseudopods. Although amoeboid motility is generally mediated through an actin-based cytoskeleton, Ascaris sperm lack this system. Instead, their major sperm protein (MSP) forms an extensive filament system that appears to fulfil this function. Because their motility appears to be essentially the same as that of their actin-rich counterparts, Ascaris sperm offer a simple alternative system for investigation of the molecular mechanism of amoeboid movement. To examine the structure and composition of the cytoskeleton, we stabilized the extremely labile native MSP filaments by detergent lysis of sperm in the presence of either glutaraldehyde or polyethylene glycol (PEG). Biochemical analysis showed that the cytoskeleton contained two isoforms of MSP, designated alpha- and beta-, that we purified and sequenced. Both contain 126 amino acids and have an acetylated N-terminal alanine, but differ at four residues so that alpha-MSP is 142 Da larger and 0.6 pH unit more basic than beta-MSP. Neither isoform shares sequence homology with other cytoskeletal proteins. In ethanol, 2-methyl-2,4-pentanediol (MPD), and other water-miscible alcohols each isoform assembled into filaments 10 nm wide with a characteristic substructure repeating axially at 9 nm. These filaments were indistinguishable from native fibers isolated from detergent-lysed sperm. Pelleting assays indicated a critical concentration for assembly of 0.2 mM for both isoforms in 30% ethanol, but alpha-MSP formed filaments at lower solvent concentration than beta-MSP. When incubated in polyethylene glycol, both isoforms formed thin, needle-shaped crystals that appeared to be constructed from helical fibers, with a 9 nm axial repeat that matched that seen in isolated filaments. These crystals probably contained a parallel array of helical filaments, and may enable both the structure of MSP molecules and their mode of assembly into higher aggregates to be investigated to high resolution.  (+info)