Ascaris.

Wang and Davis provide an overview of the parasite nematode Ascaris, including the history of its role in biological research.

[STRUCTURAL, MOLECULAR AND FUNCTIONAL FEATURES OF NEMATODE SURFACES AND THE POSSIBILITY OF ANTHELMINTIC DRUGS DEVELOPMENT (REVIEW)].

Helminthiases caused by parasitic nematodes are widespread in different regions of the world. The main adaptation for overcoming adverse conditions is a barrier properties of the cuticle surface structure, which differs from the membrane teguments of trematodes and cestodes. Different types of nematodes have specific structural and biochemical adaptations at different stages of their life cycle. While creating specific areas of habitat and nutrition, some types of parasites change the morphology and functioning of the host tissues. Ascaris suum and Caenorabditis elegans were widely used as model organisms in the study of genetics, biochemistry of nematodes. Studying of biochemistry and molecular biology of structural components of nematode surfaces is important for development of effective and safe anthelmintic drugs. The differences in the structure and functioning of transport enzymes of parasites and humans will help to create effective specific inhibitors and anthelmintic remedies. An important point of application of anthelmintic drugs can serve as inorganic ions transport proteins in the membranes of the surfaces. Glycolipids of cuticle contribute to the evasion from the host immune system, protecting the surface proteins from degradation by proteases. Study of helminth surfaces makes an important contribution to the development of anthelmintic drugs and vaccines, for helminthiasis treat.

[Nematodes of humans in the Primorye Territory].

Nematodes occupy the top in the general pattern of human parasitic diseases in the Primorye Territory. In the south of the Far East, there are a total of 28 nematode species that can parasitize man. However, the authors have identified only 8 nematode-induced diseases, such as ascariasis, enterobiasis, toxocariasis, trichocephaliasis, anisakiasis, trichinosis, dirofilariasis, dioctophymosis. The latter has been found only once in the 1920s. According to official statistical data, the proportion of ascariasis and enterobiasis accounted for 43.8 and 53.5% of the total number of helminthiases, respectively.

In situ characterisation of a microorganism surface by Raman microspectroscopy: the shell of Ascaris eggs.

Intestinal nematodes are very common human parasites and a single species, Ascaris lumbricoïdes, is estimated to infect a quarter of the world's population. A sticky external layer covers their eggs. This work shows that Raman vibrational confocal spectroscopy is able to give information on the biochemical composition of the shell of Ascaris eggs. The biochemical localised characterisation of Ascaris eggs was performed directly on the eggs in their aqueous environment. The studied parasites came from two origins: dissections of adult females and extractions from biosolid sludges. The presence of mucopolysaccharides, proteins and chitin in the shell was demonstrated. The presence of ascaroside compounds was shown particularly via the narrow and intense bands from the organised long CH2 chains. To the best of our knowledge, this is the first time that the latter have been observed in Raman vibrational spectra of microorganisms. Hydration of the shell was different depending on the intensity of the colour of the sludge eggs. Knowledge of the biochemical structural properties of egg surfaces would be useful to understand the egg adhesion phenomena on vegetables contaminated by reused wastewater.

Morphology of the uterus of Ascaris lumbricoides in the region where fertilization and formation of egg-shell occur.

Morphology of the female reproductive system of Ascaris lumbricoides L. was studied in the region starting with the junction between the oviduct and the uterus (O-U) up to the junction of both uterine branches into the vagina with regard to the process of fertilization and formation of egg-shells. In the O-U junction morphology differed in two following sections: a continuous simple squamous up to simple cuboidal epithelium, and simple cuboidal up to columnar epithelium with broad intercellular spaces leading into the lumen of the tubular reproductive organ filled with sperm. The area in the O-U junction zone was found where the wall of the organ was formed by elongated club-shaped cells attached to the common basal lamina by a narrow pedicle. Intercellular spaces thus formed "crypts" which was covered with dilated parts of cells towards the tubular lumen. Crypts were found to be filled with sperm. This area resembles the structure known as the receptaculum seminis where the stored sperm survive. Epithelial cells of the uterus are of cuboidal up to columnar shape with signs of merocrine secretion. In the distal part of the uterus the secretory active cells probably produce viscous secreta allowing the transfer of the eggs towards the vagina. The cells of the uterus wall are elongated and because of their longer axis, they are orientated longitudinally. In centripetal parts, the cell walls do not have contact with each other and form elongated, deep furrows ("canyons") through which the sperm can run against the flow of uterus content up to the junction of the O-U, where they are stored in the spermatheca-like structure. At any time they are disposal for fertilization.

Factors influencing the egg production of Ascaris lumbricoides: relationship to weight, length and diameter of worms.

Fifty children aged 6 to 13 years and infected with Ascaris lumbricoides were selected for the study. The number of eggs laid daily by a female Ascaris increased with increase in its length, weight and diameter. Female worms became mature and started laying eggs when they reached a length of 118 mm. Adult female worms measuring 3.7 mm or more in diameter were found to be mature. The minimum weight of a worm producing eggs was 1.1 g. On average the number of eggs produced by the female decreased with increase in the worm load.

The physiology and pharmacology of neuromuscular transmission in the nematode parasite, Ascaris suum.

The organization of Ascaris motoneurones and nervous system is summarized. There is an anterior nerve ring and associated ganglia, main dorsal and ventral nerve cords which run longitudinally, and a small set of posterior ganglia. Cell bodies of motoneurones are found in the ventral nerve cord and occur in 5 repeating 'segments'; each contains 11 motoneurones. Seven morphological types of excitatory or inhibitory motoneurone are recognized. Each Ascaris somatic muscle cell is composed of the contractile spindle; the bag region, containing the nucleus; the arm; and the syncytial region, the location of neuromuscular junctions. The resting membrane potential of muscle is approximately -30 mV and shows regular depolarizing, Ca-dependent 'spike potentials' superimposed on smaller Na(+)- and Ca2(+)-dependent 'slow waves' and even slower 'modulation waves'. The membrane shows high Cl- permeability. Adjacent cells are electrically coupled so that electrical activity in the cells is synchronized. Acetylcholine (ACh) and gamma-aminobutyric acid (GABA) affect the electrical activity. Bath-applied ACh increases membrane cation conductance, depolarizes the cells, alters the frequency and amplitude of spike potentials and produces contraction. Bath-applied GABA increases Cl- conductance, decreases spike activity and causes hyperpolarization and muscle relaxation. The extra-synaptic ACh receptors on the bag region of Ascaris muscle can be regarded as a separate subtype of nicotinic receptor. ACh and anthelmintic agonists (pyrantel, morantel, levamisole) produce a dose-dependent increase in cation conductance and membrane depolarization which is blocked by tubocurarine, mecamylamine but not by hexamethonium. The potency of GABA agonists, with the exception of sulphonic acid derivatives, correlates with the vertebrate GABAa receptor. The potency of antagonists does not. Thus, bicuculline, securinine, pitrazepine, SR95531 and RU5135 are potent vertebrate GABAa antagonists but have little effect on GABA receptors. The potency order of the arylaminopyridazine GABA antagonists: SR95103, SR95132, SR42666, SR95133, SR95531, SR42627 and SR42640 at the Ascaris GABA receptors contrasts with that at vertebrate GABAa receptors. It has been suggested that the receptor is referred to as a GABAn receptor. Patch-clamp studies show that ACh activates a non-selective cation channel which has a main conductance of 40-50pS and apparent mean open time of 1.3 ms; a smaller channel of 20-30 pS with a similar open-time is also activated. Pyrantel and levamisole also produce openings with similar conductances and open-times.(ABSTRACT TRUNCATED AT 400 WORDS)

Centripetal flow and directed reassembly of the major sperm protein (MSP) cytoskeleton in the amoeboid sperm of the nematode, Ascaris suum.

The cytoskeleton of the amoeboid spermatozoa of Ascaris suum consists of major sperm protein (MSP) filaments arranged into long, branched fiber complexes that span the length of the pseudopod and treadmill rearward continuously due to assembly and disassembly at opposite ends of the complexes (Sepsenwol et al., Journal of Cell Biology 108:55-66, (1989)). Examination by video-enhanced microscopy showed that this cytoskeletal flow is tightly coupled to sperm locomotion. The fiber complexes treadmilled rearward at the same rate (10-50 microns/min) as the cell crawled forward. Only fiber complexes with their plasmalemmal ends within a limited sector along the leading edge of the pseudopod underwent continuous assembly. Thus, the location of this sector, which occupies about 50% of the pseudopod perimeter, determined the direction of sperm locomotion. Treatment of sperm with agents that lower intracellular pH, such as weak acids and protonophores, caused the fiber complexes to disassemble completely in 4-5 sec. Removal of these compounds resulted in reassembly of the cytoskeleton in a pattern that mimicked treadmilling in intact sperm. The fiber complexes were reconstructed by assembly at their plasmalemmal ends so that within 30-60 sec the entire filament system reformed and the cell resumed locomotion. Both cytoskeletal reassembly and treadmilling required exogenous HCO3-. These results suggest that variation in intracellular pH may help regulate cytoskeletal treadmilling and thereby play a significant role in sperm locomotion.

Visualization of chitin-protein layer formation in Ascaris lumbricoides egg-shells.

The formation of chitin-protein layer in Ascaris lumbricoides egg-shells was studied using the method of chitin structures visualization by means of derivatives of stilbene-disulfonic acid (Blankophor, Bayer, FRG). Intensive formation of chitin structures in A. lumbricoides egg-shell occurred only in fertilized females in a very short portion of uterus from the site of connection of the oviduct with the uterus up to 25-30 mm distally, i.e. in the section forming about one fifth or less than one sixth of length of adult female uterus. Already 3 mm from the beginning of uterus there was a thin layer on the surface of the fertilized eggs which contained chitin detectable by Blankophor visualization, whereas the chitin-protein layer on the shells could not be demonstrated histologically. The thickness of this chitin-protein complex increased distally. At 25 mm from the beginning of uterus the chitin layer was already complete and its thickness did not increase any more.

Some aspects of the neuromuscular system of Ascaris.

1. The structure and physiological properties of the somatic neuromuscular system of the nematode Ascaris lumbricoides var. suum are discussed taking into account early work from this laboratory, the results of other workers, and experiments in progress. 2. Anatomically, the central feature of the somatic musculature is the presence of a specialized muscular, but not contractile, structure: the syncytium or sarcopile, formed by the terminal processes of the muscle cell arms that contact the nerve cord. In this region, they are electrically coupled to one another and form chemical synapses with the nerve fibres. 3. The syncytium serves, primarily, as a nerve-muscle manifold, or device which allows the neural control of the muscle fields with great economy in the amount of nervous tissue, numbers of chemical junctions and quantities of synaptic transmitters. 4. The structure of the syncytium is being studied with the scanning electron microscope. The results reveal the convergence of the arms on discrete sites as they approach the cords, as well as a longitudinal arrangement of the terminal processes as they course over the cords, at least in the posterior region of the animal. 5. The characteristics of the electrical coupling between the muscle cells are being investigated. A pattern has been observed that is dependent on the position of the cell pairs with respect to the longitudinal axis of the animal. 6. A study of signal propagation in the arms has revealed that the morphology of the muscle cells contributes to the extent and preferential direction of propagation.

The weight/length profiles of Ascaris lumbricoides within a human community before mass treatment and following reinfection.

Weight and length profiles are presented of 3505 Ascaris worms recovered after mass anthelmintic treatment of a human community in January 1984 and, after an 11 month period of reinfection, in November 1984. Male and female worms recovered after reinfection were significantly heavier and longer than those expelled after initial treatment (P less than 0.0001). Multiple regression models were employed to examine variability in parasite size. A positive influence of host body weight on the weight of parasites recovered in January, but not in November, was observed. No negative relationship was recorded at either date between worm size and the total number of worms harboured, even after controlling for host weight. Striking host age-related variability was observed in the distribution profile of weights and lengths of individual worms recovered in January. Children harboured predominantly smaller worms before initial treatment, while adults expelled mainly heavy worms. In contrast, worms expelled by both children and adults after reinfection were heavier and more homogeneous in size, particularly within the relatively heavily infected group. These patterns argue against a primary role for density-dependent or acquired resistance mechanisms in determining the size of Ascaris in humans. However, the results are consistent with a hypothesis initially suggested by Jung (1954) that established worms may inhibit the development of newly acquired Ascaris larvae, perhaps regulating their own abundance.

Retrovesicular ganglion of the nematode Ascaris.

The nematode nervous system is distinguished by the small number and morphological simplicity of its neurons. Recently, the shapes and synaptic interactions of each of the 302 neurons in the small free-living nematode, Caenorhabditis elegans, have been determined from reconstructions of serial sections by electron microscopy. Comparable anatomical studies of the large parasitic nematode Ascaris have concentrated on the dorsal and ventral nerve cords where reconstructions of motor neurons by light microscopy led to the identification of seven distinct types of motor neurons, each corresponding to a homologous cell type in C. elegans. In this study the shapes of the 13 neurons with cell bodies in the retrovesicular ganglion (RVG) of Ascaris suum were reconstructed from light micrographs of serial sections. In other preparations the morphology of RVG neurons was observed in whole mounts after the cells were impaled with microelectrodes and injected with the fluorescent dye Lucifer yellow. The intracellular electrodes also permitted electrical recordings and revealed that one type of cell, the AVF-like interneuron, expresses spontaneous repetitive plateau potentials. Comparisons of neuronal morphologies in the retrovesicular ganglia of Ascaris and C. elegans suggest that each neuron in Ascaris can be assigned a corresponding homolog in C. elegans. These data provide further evidence for a remarkable conservation of neuronal morphology in nematodes despite large differences in size and habitat.

Description of a new species of Thynnascaris Dollfus, 1933 (Nematoda: Anisakidae) from the stomach of the marine teleost fish Rachycentron canadus (Linnaeus).

A new species of the nematode genus Thynnascaris obtained from the teleost Rachycentron canadus (Linnaeus) is reported. A detailed examination of this specimen has allowed us to erect a new species Thynnascaris to accommodate the worm. It shows remarkable differences from other known species of Thynnascaris in respect of body size, length of the oesophageal appendix and intestinal caecum, location of nerve ring and excretory pore, on the papillae on the lips arrangement, type of the striations on the cuticle, vulva position, arrangement of caudal papillae and size of the spicules. The new species is designated as Thynnascaris shyamasundarii.

Ascaris suum: partial isolation and characterization of hypodermis from the adult female.

A method was developed to remove the muscle from body wall strips of adult female Ascaris suum resulting in a hypodermis cuticle preparation. Optimum treatment for obtaining the hypodermis cuticle was a 15 min incubation with trypsin (2.0 mg/ml) at room temperature, followed by mechanical removal of the muscle. The hypodermis cuticle prepared in this manner incorporated radiolabeled amino acids into cuticular and hypodermal proteins; incorporation was inhibited by protein synthesis inhibitors. Characterization of the hypodermal proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the hypodermis apparently contains proteins that differ from those of the cuticle and that the hypodermis of adult A. suum appears to lack cuticle protein precursors. This result will now allow detailed biochemical and physiological investigations of the hypodermis, a tissue which is critical for cuticle synthesis.

Fatal human ascariasis following secondary massive infection.

More than 796 Ascaris lumbricoides worms weighing 550 g were recovered at autopsy from a 2-year-old black South African girl. Most of the worms were taken from necrotic small intestine, but worms were also in the stomach, esophagus, intrahepatic and extrahepatic bile ducts, and gallbladder. The worms had caused torsion and gangrene of the ileum, which was interpreted as the cause of death. Worms were formalin-fixed and individually weighed. There were 796 intact worms and 112 appreciably large (greater than 0.2 g) fragments of worms. Statistical analysis of the weights revealed 2 distinct populations of worms: 16 large worms (0.5-2.3 g) and 778 small worms (0.03-0.95 g). The difference in weight between these 2 groups of worms was significant (male and female worms treated separately; P less than 0.05 to P less than 0.001). These observations reveal that the patient acquired a massive and fatal infection with A. lumbricoides while hosting a relatively burden.

Synaptic inhibition and cell communication; impairment of cell-to-cell coupling produced by gamma-aminobutyric acid (GABA) in the somatic musculature of Ascaris lumbricoides.

The influence of gamma-aminobutyric acid (GABA) (10(-5) M) on the electrical coupling of giant somatic muscle cells of Ascaris lumbricoides was investigated. GABA enhanced the resting potential of the cells and abolished the spike activity. The coupling coefficient (V2/V1) was reduced by 58.8% while the input resistance (Rin) was decreased by 38.8%. The decline in Rin was not related to unlinearity of the current-voltage relation. As the time constant of cell membrane was reduced by 28.4% by the addition of GABA the effect of the neurotransmitter on cell-to-cell coupling seems to be mainly related to a decrease in resistance of the non-junctional membrane due to an increase in chloride conductance.

Reinfection and infection rates of ascariasis in relation to seasonal variation in the Philippines.

Stool examinations of 320 primary school children for eggs of Ascaris revealed a prevalence of 74.0 percent. Reinfection and infection rates were determined on a monthly basis with egg-positive subjects treated correspondingly. Due to dropouts of subjects, only 154 children completed the 12-month observation. About 15% of children remained negative after treatment during one year but 85% got reinfected, with those reinfected only once being the highest then those reinfected twice, followed by those reinfected more than twice in a year. Of the 203 Ascaris worms collected 69% were females and 31% were males with a sex ratio of 2.4 females to one male; 73% were mature and 27% were immature females; 70% were mature and 30% were immature males; mean number of worms per child was 2.6. The mean length and weight of female was 22.9 cm and 3.6 gms respectively while for males it was 16.1 cm and 1.7 gm respectively. The graph showing amount of rainfall, reinfection and infection rates of ascariasis revealed the presence of two major peaks both in the reinfection and infection rates noted in December-January and May-June. Likewise, the rainfall also peaked twice namely in August and October. It appears that ascariasis reinfection or transmission is highest when rainfall is minimal and lowest when rainfall is at its highest peak. Based on the peaks of reinfection and infection, it is suggested the school children be dewormed in June and in December each year for at least three years.

Changes in the somatic musculature of the 4th-stage larvae of Ascaris suum Goeze, 1782 (Nematoda: Ascaridoidea) developing in swine.

Fourth-stage larvae of Ascaris suum, recovered from piglets at 11-22 days post-infection (p.i.), were examined by light microscopy for changes in the somatic musculature. During this time the estimated total number of muscle cells in the body increases from approximately 600 to 21 000 cells. This non-eutelic development appears to occur by division of platymyarian muscle cells into coelomyarian cells, thereby increasing the number of muscle cells/quadrant from 5 to 85. The incompleteness of these divisions results in sarcoplasmic connections among muscle cells, and between muscle cells and nerve chords. At 11 days p.i., immediately after the 3rd moult, the variation in muscle cell length in a quadrant, with the longest cells being at the lateral chords, has been established. The average muscle cell length at this point is 0.101 mm, the longest is 0.164 mm. These values have increased to 0.365 mm and 1.122 mm, respectively, by 22 days p.i. At 18 days p.i. those cells in the posterior section of the larva are still the shortest in the body.

Factors contributing to the in vitro development of Ascaris suum from second-stage larvae to mature adults.

When a three-step roller culture system was used, second-stage larvae of Ascaris suum, artificially hatched from eggs, developed in high numbers to the fourth stage, and a few to young and mature adults. The culture system consisted of (1) Medium KW-2 supplemented with 10 mM L-cysteine for the first 4 days, and with 5 mM L-cysteine for the following 7 days; (2) followed by Medium API-18 for 7 days; and (3) thereafter, by Medium API-1 supplemented with hemin (bovine) at a concentration of 24 micrograms/m1. Cultures were gassed with 95% nitrogen-5% carbon dioxide for the first 4 days and 85% nitrogen-5% oxygen-10% carbon dioxide thereafter, and incubated at 39 C. Two mature females that produced unfertilized eggs and a mature male with spermatozoa were the most advanced stages attained. The mature females were obtained in 67 and 73 days; and the largest female measured 110 mm. The latter produced 1,356,000 unfertilized eggs, from days 67 to 125. The mature male was obtained in 80 days; it measured 77 mm long and had paired spicules that were 1.5 mm long. Development of A. suum in three other culture systems showed that deletion of Medium API-18 or its substitution by Medium KW-2 limited development to late fourth stage and early, young adults, respectively; and the use of Medium API-1 without hemin limited development to early fourth stage.