Description of Saccocoelioides miguelmontesi n. sp. (Digenea: Haploporidae) from characid fishes in the Iguazu River Basin based on morphological and molecular evidence.

Here we describe a new species of the genus Saccocoelioides found parasitizing Astyanax dissimilis Garavello & Sampaio, Psalidodon bifasciatus (Garavello and Sampaio) and Bryconamericus ikaa Casciotta, Almirón & Azpelicueta from the Iguazu National Park, Misiones province, Argentina. Saccocoelioides miguelmontesi n. sp. was studied based on morphological and molecular (28S rDNA and COI mtDNA sequences) data. The COI mtDNA tree indicated that the specimens collected from the three fish hosts are conspecific, with an intragroup p-distance of 0%. The new species shows an intermediate morphological configuration between the diminutive and robust forms described for Saccocoelioides by Curran (2018). Although, in the 28S rDNA tree, it is placed in a well-supported clade with the two robust species analysed (S. elongatus and S. magnus; p-distance of 1 and 2%, respectively), it differs from the robust group by the range of body size, mature egg size, oral and ventral sucker size, sucker ratio, oral sucker to pharynx ratio, and post-cecal or post-testis/body length percentage. Our results led us to redefine the robust group as having eggs shorter or equal in length to the pharynx. Saccocoelioides miguelmontesi n. sp. the 10th species reported from Argentina and the 7th species within the robust group.

Metacercariae in the brain of Erythrinus cf. erythrinus (Characiformes: Erythrinidae) from Iguazú National Park (Argentina): do they belong to Dolichorchis lacombeensis (Digenea, Diplostomidae)?

In Argentina, the family Diplostomidae is composed of eight genera: Austrodiplostomum Szidat & Nani; Diplostomum von Nordmann; Dolichorchis Dubois; Hysteromorpha Lutz; Neodiplostomum Railliet; Posthodiplostomum Dubois; Sphincterodiplostomum Dubois; and Tylodelphys Diesing. During a parasitological survey of fishes from the Iguazú National Park we detected diplostomid metacercariae in the brain of Erythrinus cf. erythrinus. Fish were caught using crab traps, transported alive to the field laboratory, cold-anaesthetized and euthanized by cervical dissection. Some metacercariae were heat-killed in water and fixed in 10% formalin and others were preserved in alcohol 96% for DNA extraction. They were sequenced for the partial segment of the 28S rDNA, internal transcribed spacer (ITS) rDNA and cytochrome c oxidase subunit I (COI) mtDNA genes. Phylogenetic reconstruction was carried out using Bayesian inference and the proportion (p) of absolute nucleotide sites (p-distance) was obtained. In the 28S rDNA tree, the metacercaria sequenced grouped as Dolichorchis sp. The COI mtDNA p-distance between the metacercariae with Dolichorchis lacombeensis was 0.01. There is a small number of ITS sequences for the Diplostomidae family deposited in the GenBank. The oral sucker, ventral sucker, holdfast organ and the distance between oral and ventral suckers are larger in the adult compared with the metacercariae. Additionally, hind-body length and width are larger in the adult due to the development of the genital complex. Further studies using an integrative approach will help confirm the affiliation of other species to the genus Dolichorchis.

Ecology of fleas and their hosts in the trifinio of north-east Argentina: first detection of Rickettsia asembonensis in Ctenocephalides felis felis in Argentina.

Fleas are important in public health due to their role as parasites and vectors of pathogens, including Rickettsia. The aim of this study was to evaluate the diversity, abundance and prevalence of fleas and the presence of Rickettsia in the trifinio of north-east Argentina. Fleas from household and synanthropic animals were obtained from urban and periurban areas. They were taxonomically identified and samples of 227 fleas in 86 pools were analysed by polymerase chain reaction targeting the gltA and ompB genes of Rickettsia spp. The study revealed that Ctenocephalides felis felis was dominant on dogs, cats and opossums, with higher prevalence in the periurban area. The Shannon-Wiener and Morisita-Horn indices expressed differences in the diversity and similarity values of the absolute abundances of the species between the areas compared. DNA amplifications revealed 30.8% C. f. felis pools positive for Rickettsia spp. Phylogenetic analysis showed that the haplotype obtained was identical to Rickettsia asembonensis from Peru and Brazil. This is the first detection in Argentina of R. asembonensis that infects C. f. felis, and we emphasize the importance of conducting research from a 'One Health' perspective on the role of opossums and rodents in the integration of the transmission cycles of rickettsial bacteria.

Prosthenhystera gattii n. sp. (Digenea: Callodistomidae), a gallbladder parasite of Bryconamericus ikaa from the lower Iguazú River, described based on combined molecular and morphological evidence.

Adult forms of members of the Callodistomidae always parasitize the gallbladder of freshwater fishes and occur in Africa and America. This study provides a description of a new South American species belonging in Prosthenhystera from the gallbladder of a characid fish (Bryconamericus ikaa), and ribosomal gene sequences (28S rDNA and ITS1-5.8S-ITS2) are used to demonstrate molecular differences between the new species and congeners as well as explore interrelationships among congeners. Additionally, the first cytological analysis is conducted for a member of the family to determine chromosome number and arrangement. Prosthenhystera gattii n. sp. most closely resembles Prosthenhystera caballeroi in morphology, but the vitellarium is more extensive reaching anterior to the caecal bifurcation in the new species and the uterus is confined to the hindbody in P. gattii n. sp., whereas it extends to the level of the pharynx in P. caballeroi. Also, the testes, cirrus sac, seminal receptacle and the ratio of body length to width are larger in P. gattii n. sp. Independent Bayesian inference analyses of 28S rDNA and ITS1-5.8S-ITS2 sequence fragments produced phylograms that showed P. gattii n. sp. is more similar to Prosthenhystera obesa + Prosthenhystera oonastica than P. caballeroi + two unidentified species of Prosthenhystera, but with poor posterior probability support for the node in the ITS1-5.8S-ITS2-based phylogram. Further, the genetic distance between P. oonastica and P. gattii n. sp. are the largest among Prosthenhystera spp. Cytological analysis revealed ten metacentric chromosomes, which is fewer than the 12-18 chromosomes present in species from the closely related Gorgoderidae.

Pathology associated with three new Clinostomum metacercariae from Argentina with morphological and DNA barcode identification.

In the Laboratory of Parasites of Fishes, Crustaceans and Mollusks (CEPAVE), we undertook a parasitological study on three species of fish from the Espinal and Esteros del Iberá ecoregions of Argentina. Clinostomid metacercariae were found parasitizing Characidium rachovii, Crenicichla vittata and Gymnogeophagus balzanii. In this study, we analysed the damage that these parasites inflict on their hosts through the evaluation of histological sections. In addition, Clinostomum metacercariae were identified using morphological characters and DNA barcoding. In the pathological analysis, we observed that muscle tissue was the most affected. The inflammatory response showed vascular congestion areas and infiltration of numerous inflammatory cells, mainly lymphocytes. The molecular and morphological approach supports the presence of three new lineages of clinostomid metacercariae in Argentina. This could lead to the discovery of a high number of lineages or species of Clinostomum from South America.

Cholestanol-loaded-cyclodextrin improves the quality of stallion spermatozoa after cryopreservation.

This study was to compare the effect of adding cholesterol or cholestanol loaded cyclodextrins in stallion sperm prior to cryopreservation to optimize sperm cryosurvival. Ejaculates from each of eight stallions were diluted to 120 million cells in a S-MEDIUM diluent. The diluted sperm were sub-divided into three treatments: no additive (control); 0.75mg of cyclodextrin pre-loaded with cholesterol (CLC)/120 million sperm (positive control); 1.5mg CLC/120 million sperm; 0.75mg of cyclodextrin pre-loaded with cholestanol (CnLC)/120 million sperm; and 1.5mg CnLC/120 million sperm. To set the experiments, the treated sperm were incubated for 15min at 22°C to allow for the incorporation of cholesterol or cholestanol. In each experiment, treated sperm incubated for 15min at 22°C to allow for incorporation of cholesterol or cholestanol. The samples were then diluted 1:5 (v/v) with Lactose-Egg Yolk diluent and cooled to 5°C over a 2h period. Loaded into 0.25ml polyvinylchloride straws, frozen in liquid nitrogen vapor for 10min, and then plunged into liquid nitrogen until further use. Higher percentages of motile sperm and viable cells were achieved after thawing for stallion sperm treated with CLC and CnLC compared to control (P<0.05). Addition of CnLC also resulted in more number sperm binding to chicken egg perivitelline membrane (CEPM) after cryopreservation than cholestanol and control sperm (P<0.05). In conclusion, CnLC and CLC improved the percentage of post-thaw motility of equine sperm and CnLC provided greater binding efficiency.

The search for new antimalarial drugs from plants used to treat fever and malaria or plants ramdomly selected: a review.

In this review we discuss the ongoing situation of human malaria in the Brazilian Amazon, where it is endemic causing over 610,000 new acute cases yearly, a number which is on the increase. This is partly a result of drug resistant parasites and new antimalarial drugs are urgently needed. The approaches we have used in the search of new drugs during decades are now reviewed and include ethnopharmocology, plants randomly selected, extracts or isolated substances from plants shown to be active against the blood stage parasites in our previous studies. Emphasis is given on the medicinal plant Bidens pilosa, proven to be active against the parasite blood stages in tests using freshly prepared plant extracts. The anti-sporozoite activity of one plant used in the Brazilian endemic area to prevent malaria is also described, the so called "Indian beer" (Ampelozizyphus amazonicus, Rhamnaceae). Freshly prepared extracts from the roots of this plant were totally inactive against blood stage parasites, but active against sporozoites of Plasmodium gallinaceum or the primary exoerythrocytic stages reducing tissue parasitism in inoculated chickens. This result will be of practical importance if confirmed in mammalian malaria. Problems and perspectives in the search for antimalarial drugs are discussed as well as the toxicological and clinical trials to validate some of the active plants for public health use in Brazil.

Capsaicin prevents the adrenocorticotropin-induced improvement of cardiovascular function and survival in hemorrhage-shocked rats.

A volume-controlled hemorrhagic shock was produced in anesthetized rats by intermittent bleeding from an iliac vein over a period of 20-30 min, until the carotid mean arterial pressure (MAP) stabilized around 20-24 mmHg. In this condition, which caused the death of all saline-treated animals within 25-30 min, the intravenous (i.v.) bolus injection of the adrenocorticotropin fragment 1-24 (ACTH(1-24)) at a dose of 160 micrograms/kg promptly restored MAP, as well as pulse pressure, heart rate and respiratory function, and greatly prolonged the survival time. Capsaicin (125 mg/kg cumulatively, s.c., 1 week before) completely prevented the anti-shock effect of ACTH(1-24), which, on the other hand, was shared by i.v. [Nle11]-substance P (SP) (200-300 micrograms/kg). Finally the SP-antagonist [D-Arg1,D-Pro2,D-Trp7,9,Leu11]-SP prevented the effect of ACTH(1-24). These results suggest that SP-containing nerve fibers are required for the effect of ACTH in hemorrhagic shock.

Reversal of experimental hemorrhagic shock by dimethylphenylpiperazinium (DMPP).

In a rat model of hemorrhagic shock which caused the death of all control rats within 30 min, i.v. injection of the ganglion-stimulating drug dimethylphenylpiperazinium (DMPP) caused a dose-dependent reversal of the shock condition--without the need for reinfusion of the shed blood--starting from the dose of 4 ng/kg i.v. Shock reversal was associated with the mobilization of residual blood and improvement in blood flow, particularly at the carotid level. These results could influence our thinking on pathophysiology and first-aid management of shock.

A method for screening drugs against the liver stages of malaria using Plasmodium gallinaceum and Aedes mosquitos.

1. The radical cure of human malaria caused by Plasmodium vivax requires two drugs, i.e., a blood schizontocide such as chloroquine to clear the circulating parasites, and primaquine aimed at the liver stages (hyponozoites) responsible for the late relapses of this parasite. Primaquine is unique as a radical curative drug but is highly toxic. The only useful model currently available for screening drugs to replace primaquine is Plasmodium cynomolgi-induced malaria in Rhesus monkeys. Because of the limited availability and cost of these animals, the development of non-primate models for such screening would be of considerable value. 2. We used a drug-screening assay for the liver stage malaria parasite based on the ability of such drugs to stop development of gametocytes in the mosquito vector. The inhibition of the sporogonic cycle of malaria in the mosquito by primaquine (15 mg/kg) was confirmed here and used for re-evaluation of the gametocyte method. 3. We observed that the level of parasitemia in the untreated control chicken used to infect mosquitos was a crucial factor affecting the subsequent development of sporogony. Thus, parasitemia was carefully controlled in the studies involving oocyst development. Parasitemias lower than 6% at the beginning of the experiment and increasing were found to be most appropriate for the production of the infectious gametocytes during a period of 8 h.(ABSTRACT TRUNCATED AT 250 WORDS)

A method for screening drugs against the liver stages of malaria using Plasmodium gallinaceum and Aedes mosquitos

The radical cure of human malaria caused by Plasmodium vivax requires two drugs, i.e., a blood schizontocide such as chloroquine to clear the circulating parasites, and primaquine aimed at the liver stages (hypnozoites) responsible for the late relapses of this parasite. Primaquine is unique as a radical curative drug but is highly toxic. The only useful model currently available

Nicotine reverses hemorrhagic shock in rats.

Cholinergic mechanisms are currently thought to play an essential role in blood pressure homeostasis. Here we show that, in urethane-anaesthetized rats bled to severe hemorrhagic shock, the i.v. administration of nicotine 0.2-50 micrograms/kg causes a prompt, sustained and dose-dependent improvement in cardiovascular and respiratory functions, the animals' survival rate being significantly higher than that of animals treated with saline. These effects are prevented by bilateral cervical vagotomy and by concurrent local anaesthesia of the carotid bodies, which suggests that stimulation of visceral afferents is the main mechanism of action of nicotine in hemorrhagic shock.

Early treatment with ACTH-(1-24) in a rat model of hemorrhagic shock prolongs survival and extends the time-limit for blood reinfusion to be effective.

The ability of ACTH-(1-24) to prolong survival and to extend the deadline for effective blood reinfusion has been studied in a model of lethal hypovolemic shock in the rat. Anesthetized rats were bled to a mean arterial pressure of 18 to 25 mm Hg and then subjected to one of the following iv treatments: a) saline; b) ACTH-(1-24), 160 micrograms/kg; c) blood reinfusion; d) ACTH-(1-24), 160 micrograms/kg; c) blood reinfusion; d) ACTH-(1-24), with saline 5 min after bleeding died within 0.05 h. On the other hand, the treatment with ACTH-(1-24) induced an almost complete and sustained recovery of cardiovascular and respiratory functions associated with a survival time of 44 +/- 18 h, while four of six rats reinfused with the withdrawn blood were still alive 15 days later. The time-lapse between bleeding and treatment was of crucial importance, and neither ACTH-(1-24) injection nor blood reinfusion had any effect if performed 25 min after bleeding. However, treatment with ACTH-(1-24) shortly after bleeding (5 min) greatly improved the effect of a later blood reinfusion. These data indicate that ACTH-(1-24) can prolong survival and permit the time-lapse between blood loss and blood reinfusion to be extended.

Circulatory and respiratory consequences of massive hemorrhage are reversed by protoveratrines.

In a rat model of severe hypotension and respiratory depression induced by step-wise bleeding, protoveratrines cause a prompt and sustained improvement of cardiovascular and respiratory functions, both in anesthetized and in conscious animals, seemingly through a magnification of the reflex response originated by the chemoreceptors of aortic and carotid bodies. The restoration of cardiovascular function is attributable to an increase both in total peripheral resistance and cardiac output. The finding could provide the basis for a new approach to the first-aid management of massive blood losses.

The adrenocorticotropic hormone (ACTH)-induced reversal of hemorrhagic shock.

Adrenocorticotropic hormone (ACTH), while having negligible effects on cardiovascular function in the intact animal, induces a potent and sustained reversal of an otherwise invariably, rapidly fatal condition of hemorrhage-induced hypovolemic shock, in rats and dogs. The main site(s) of action are at the peripheral level; however, subsidiary site(s) of action in the CNS cannot be excluded. The studies on the mechanism of action indicate that the ACTH-induced reversal of hemorrhagic shock (a) is an extra-hormonal, adrenal-independent effect, because it is not affected by adrenalectomy and is shared by many ACTH-fragments practically devoid of corticotropic activity; (b) is antagonized by morphine in a surmontable way; (c) needs the functional integrity of the sympathetic nervous system (it is prevented by guanethidine, reserpine, and clonidine) and the availability of peripheral alpha-adrenoceptors (it is antagonized by dibenamine, prazosin and yohimbine, but not by practolol); (d) requires the integrity of afferent vagal fibers (it is almost completely abolished by vagotomy); (e) involves central cholinergic networks (it is antagonized by atropine sulphate, but not by atropine methyl bromide; and it is prevented by the intracerebroventricular injection of hemicholinium-3); (f) is associated with a massive increase in the volume of circulating blood, likely due to a mobilization from peripheral pooling sites (it is largely prevented by splenectomy or by suprahepatic veins ligature, and is associated with a restoration of the venous blood flow in peripheral vascular beds and with a normalization of venous PO2); (g) is associated with a restoration of heart and spleen adrenoceptors, whose number is significantly decreased during hemorrhagic shock. The survival time of hemorrhage-shocked animals, which is 26 +/- 3 min in controls, is greatly prolonged (44 +/- 18 h) by ACTH, provided that the treatment is made within 5-10 min after bleeding. Finally, in animals treated with ACTH within 5-10 min after bleeding, blood reinfusion retains its effectiveness and reverse shock even if performed 2-5 h later.

Adrenocorticotropic hormone (ACTH) and centrally-acting cholinomimetic drugs improve survival of rats with severe hemorrhagic shock through distinct central cholinergic mechanisms.

Pharmacological doses (40-160 micrograms/kg) of adrenocorticotropic hormone (ACTH) intravenously injected to urethane-anesthetized rats subjected to otherwise lethal hemorrhagic shock (mean arterial pressure stabilized at 20-25 mmHg) promptly restore blood pressure to about the pre-bleeding values, and prevent death (anti-shock effect). Hemicholinium-3 (i.c.v. injected) and atropine sulphate, but not atropine methylbromide, antagonize these ACTH effects. Moreover, since pirenzepine, injected i.v. or i.c.v., does not affect the anti-shock activity of ACTH, the central cholinergic mechanism participating in this ACTH action must involve M2, but not M1 brain muscarinic receptors. Intravenous physostigmine, too (but not neostigmine) and oxotremorine have an ACTH-like anti-shock effect, which however is neither affected by hemicholinium-3, nor by atropine methylbromide, nor by atropine sulphate, but only by high i.c.v. doses of gallamine or pancuronium. On the other hand, reserpine, guanethidine, and alpha-adrenoceptor blocking drugs inhibit the anti-shock effect of ACTH as well as that of oxotremorine and physostigmine. It is suggested that, in rats, both ACTH and cholinergic drugs must activate a central cholinergic mechanism(s) in order to exert a sympathetic nerve-mediated anti-shock effect. However, receptors involved are of the muscarinic M2 subtype in the case of ACTH, and probably nicotinic in the case of cholinergic drugs. That ACTH and cholinergic drugs activate different central cholinergic mechanisms is also suggested by the fact that cholinergic drugs have a centrally-mediated hypertensive action in normal animals, which is not shared by ACTH.

Reversal of haemorrhagic shock in rats by cholinomimetic drugs.

1. In an experimental model of haemorrhagic shock resulting in the death of all rats within 20-30 min, the intravenous (i.v.) injection of the tertiary amine cholinesterase inhibitor physostigmine (17-70 micrograms kg-1) induced a prompt, sustained and dose-dependent improvement of cardiovascular and respiratory function, with marked increase in the volume of circulating blood and survival of all treated animals, at least for the 2 h of observation. 2. Similar results were obtained with the i.v. injection of the cholinoceptor agonist oxotremorine (5-25 micrograms kg-1), while neostigmine (54 or 70 micrograms kg-1), a quaternary cholinesterase inhibitor which cannot cross the blood-brain barrier, had negligible effects. 3. The anti-shock activities of oxotremorine and physostigmine were blocked by the intracerebroventricular injection of either of the combined nicotinic and M2-muscarinic receptor antagonists gallamine and pancuronium, or of the nicotinic antagonist mecamylamine. They were also blocked by intraperitoneal injection of the adrenergic neurone blocking agent guanethidine, but they were not antagonized by either the combined M1- and M2-muscarinic receptor antagonist atropine, the M1-muscarinic receptor antagonist pirenzepine, or the M2-muscarinic receptor 4-diphenylacetoxy-N-methylpiperidine methobromide. 4. It is concluded that cholinomimetic drugs can reverse hypovolaemic shock through central activation (seemingly mediated by nicotinic receptors) of sympathetic tone, with mobilization and redistribution of the residual blood.

Effect of colchicine on micturition reflex in rats.

Intracerebral or intraspinal cord, but not intraperitoneal, injection of low doses of colchicine in rats induces specific toxic symptoms. This paper deals in particular with the effect of colchicine on micturition. After the injection of 5-25 micrograms/rat in cerebral ventricle or 2.5-20 micrograms/rat intraspinal cord, bladder content was markedly increased, due to a dramatic urine retention. Time of latency of vesical retention was related to the dose and to the route of colchicine administration. Cystometrographic analyses were performed in control and treated rats at various intervals of time after the injection: bladder tone, as expressed by the delta P/delta V ratio, monitored from 12 to 120 hr after colchicine injection, decreased more and more during time, suggesting that the observed vesical hypotonicity is an irreversible phenomenon.

Involvement of the sympathetic nervous system in the cardiovascular effects of ACTH-(1-24) during hemorrhagic shock in rats.

In urethane-anesthetized rats, removal of about 50% of the total blood volume over a period of 25-30 min caused hypovolemic shock, with extreme hypotension (MAP = 18-25 mm Hg and death of all animals within 22 +/- 5 min. The i.v. injection of ACTH-(1-24) in the dose range of 40-160 micrograms/kg induced a sustained, dose-dependent, and, at the highest dose used, an almost complete recovery of blood pressure, and 100% survival, at least for 2 h after treatment. The effect of ACTH-(1-24) was completely prevented by reserpine (5 mg/kg) and clonidine (0.1 mg/kg), significantly reduced by prazosin (0.1 mg/kg), dibenamine (15 mg/kg) and i.v. yohimbine (1 mg/kg) and unaffected by i.c.v. yohimbine (0.2 mg/kg) and i.v. practolol (15 mg/kg). These data suggest that the effect of ACTH-(1-24) in hypovolemic shock depends on the functional integrity of the sympathetic nervous system and is mediated through an activation of peripheral alpha-adrenoceptors.