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Background: Macracantorhincosis is a zoonotic disease resulting from inadequate sanitary conditions, which occurs in pigs infected by acanthocephalic helminths called Macracanthorhynchus hirudinaceus. The eggs of these parasites are resistant to cold, high temperatures and can survive up to 3 years in the soil. They are consumed by dung beetles of the Scarabeidae family causing the parasite to evolve into its infective form, the cystacanth. The pig becomes infected after ingestion of either larvae or adult forms of these coleoptera. This work describes a case report of macracantorhincosis found in a pig from the canton of Zaruma located in the province of El Oro, Ecuador. Case: One sow, approximately 24-month-old, weighing 30 kg, presented cachexia, muscle weakness, pale oral and ocular mucosa and a body temperature above 39.4°C. The animal had a bulge on the ventral side of the neck, which evolved causing progressive discomfort to the point that the animal stopped eating. The sow was dewormed for 3 consecutive days. Fifteen days later, the animal had convulsions and muscle tremors, and died some hours after the symptoms started. During necropsy procedure, pale digestive tract membranes and nodules with fibrin were observed in the small intestine (jejunum), which was incised and the presence of parasites adhered to the granulomas detected. Two granulomas for morphological and histological studies and stool samples for coproparasitic test were collected. The collected parasites were fixed in a 10% buffered formalin solution, cross-sections were made and routinely processed for histological studies. The 5 μm thick sections were stained using the hematoxylin and eosin (HE) technique. The parasite’s action involves perforation of the intestinal wall though its proboscis causing peritonitis and enteritis. Other conditions in intestinal dissection such as necrotic areas, inflammation of the submucosa and adult parasites adhered to the intestinal mucosa were also observed. The coproparasitic examination was performed using the flotation and sedimentation techniques. The coproparasitic test detected dark colored feces, semi-solid consistency and the presence of Macracanthorhynchus hirudinaceu eggs. In the histological evaluation of the cross section of the parasite, the presence of circular and longitudinal muscle fibers and lemniscus with their constrictor muscles was observed. Cuticle, hypodermis with tapered fibers and a large number of developing mature eggs were also reported. Discussion: There is no pathognomonic symptomatology about this parasitosis and peritonitis can be generated by intestinal perforations. The findings at necropsy were ulcerations, inflammation in the small intestine and the presence of numerous nodules in the serous layer, where there was penetration of the parasite’s proboscis. When fixed to the mucosa, these parasites cause ulcerations, inflammation and necrosis in the wall of the small intestine. The hypodermic layer is thicker than the muscular layer and the presence of leminis with their constricting muscles are typical features of acanthocephalus. It is considered appropriate to carry out epidemiological studies on the prevalence of the parasite Macracanthorhynchus hirudinaceus at pig farming system in the region, in order to determine the main risk factors. In Ecuador, cases of this disease in humans have not yet been reported, but have already been described in other countries, so the presence of this parasite in family swine farming may be considered a zoonotic-type risk factor. [ABSTRACT FROM AUTHOR]

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Peanut lectin binds to a subpopulation of mitochondria-rich cells in the rainbow trout gill epithelium. Am J Physiol Regulatory Integrative Comp Physiol 281: R1718-R1725, 2001.--Fluorescently labeled peanut lectin agglutinin (PNA-FITC) was used to identify a subtype of mitochondria-rich (MR) cells in the gills of freshwater rainbow trout. In situ binding of PNA-FITC was visualized by inverted fluorescence microscopy and found to bind to cells on the trailing edge of the filament epithelium as demonstrated by differential interference contrast optics. The amount of PNA-FITC binding on the filament epithelium increased with cortisol pretreatment concomitant with an increased chloride cell fractional area as demonstrated by scanning electron microscopy. Dispersed gill cells were isolated by trypsinization and separated using a discontinuous Percoll density gradient. Cells migrating to the 1.06-1.09 g/ml interface were found to be MR as demonstrated by staining with the vital mitochondrial dye 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide and transmission electron microscopy (TEM). However, only ~40% of the MR cells were found to bind PNA-FITC. Cortisol pretreatment increased the relative numbers of MR cells isolated from the dispersed gill cell population, but the relative proportions of PNA binding cells remained unchanged. Ultrastructural analysis of isolated cells in the TEM demonstrated that the MR cell fraction was comprised of a mixed population of chloride cells and pavement cells. chloride cells; pavement cells; peanut lectin; peanut lectin agglutinin; scanning electron microscopy; transmission electron microscopy; fish

The lack of a suitable flat epithelial preparation isolated directly from the freshwater fish gill has led, in recent years, to the development of cultured gill epithelia on semipermeable supports. To date, their minimal capacity to actively transport ions has limited their utility as ionoregulatory models. The current study describes a new method of culturing gill epithelia consisting either of an enriched population of pavement (PV) cells or a mixed population of PV cells and mitochondria-rich (MR) cells from the gills of adult rainbow trout. Although the cell culture approach is similar to the double-seeded insert (DSI) technique described previously, it makes use of Percoll density centrifugation to first separate populations of PV and MR cells, which are then seeded on cell culture supports in varying proportions on successive days so as to produce preparations enriched in one or the other cell types. Based on rhodamine staining, the MR cell-rich epithelia exhibited a threefold higher enrichment of MR cells compared to traditional DSI preparations. In general, MR cell-rich epithelia developed extremely high transepithelial resistances (TER; >30 kΩ cm2) and positive transepithelial potentials (TEP) under symmetrical conditions (i.e., L15 medium on both apical and basolateral sides). Apical exposure of cell cultures to freshwater reduced TER and produced a negative TEP in all the epithelial preparations, although MR cell-rich epithelia maintained relatively high TER and negative TEP for over 2 d under these asymmetrical conditions. Measurement of unidirectional Na+ fluxes and application of the Ussing flux ratio criterion demonstrated active Na+ uptake in PV cell-rich and MR cell-rich epithelia under both symmetrical and asymmetrical conditions. In comparison, Ca2+ uptake and Na+/K+-ATPase activity were significantly elevated in MR cell-rich preparations relative to the traditional DSI or PV cell-rich cultures under symmetrical conditions. This new methodology enhances our ability to tailor cultured gill epithelia on semipermeable supports with different proportions of PV cells and MR cells, thereby illuminating the ionoregulatory functions of the two cell types. [ABSTRACT FROM AUTHOR]

Na+ and Ca2+ regulation were compared in two euryhaline species, killifish (normally estuarine-resident) and rainbow trout (normally freshwater-resident) during an incremental salinity increase. Whole-body unidirectional fluxes of Na+ and Ca2+, whole body Na+ and Ca2+, and plasma concentrations (trout only), were measured over 1-h periods throughout a total 6-h protocol of increasing salinity meant to simulate a natural tidal flow. Killifish exhibited significant increases in both Na+ influx and efflux rates, with efflux slightly lagging behind efflux up to 60% SW, but net Na+ balance was restored by the time killifish reached 100% SW. Whole body Na+ did not change, in agreement with the capacity of this species to tolerate daily salinity fluctuations in its natural habitat. In contrast, rainbow trout experienced a dramatic increase in Na+ influx (50-fold relative to FW values), but not Na+ efflux between 40 and 60% SW, resulting in a large net loading of Na+ at higher salinities (60–100% SW), and increases in plasma Na+ and whole body Na+ at 100% SW. Killifish were in negative Ca2+ balance at all salinities, whereas trout were in positive Ca2+ balance throughout. Ca2+ influx rate increased two- to threefold in killifish at 80 and 100% SW, but there were no concomitant changes in Ca2+ efflux. Ca2+ flux rates were affected to a larger degree in trout, with twofold increases in Ca2+ influx at 40% SW and sevenfold increases at 100% SW. Again, there was no change in Ca2+ efflux with salinity, so plasma Ca2+ concentration increased in 100% SW. As the killifish is regularly submitted to increased salinity in its natural environment, it is able to rapidly activate changes in unidirectional fluxes in order to ensure ionic homeostasis, in contrast to the trout. [ABSTRACT FROM AUTHOR]

Mitochondria-rich cells (MR cells) of the gills of rainbow trout undergo changes in relative distribution and biochemical function during acclimation to partialstrength (10‰) and full-strength (30‰) seawater. In isolated total gill cells, Na+/K+-ATPase activity increased fivefoid and H+-ATPase activity decreased fourfold when trout were acclimated to either 10&permi;; or 30‰ seawater. When total MR gill cells were separated based on differential binding to peanut lectin agglutinin (PNA), the PNA subtypes underwent a change in relative distribution in seawater-acclimated fish. In freshwater, the ratio of PNA-:PNA+ was 65:35 while in seawater the distribution changed to 20:80 PNA-:PNA+. Additionally, differential changes in Na+/K+-ATPase and H+-ATPase activity in each of the independent cell types occurred during seawater acclimation; Na+/K+-ATPase activity in the PNA- cells increased by 197% while in PNA+ cells Na+/K+ATPase decreased by 57%. However, H+-ATPase activity was decreased in both PNA- (84%) and PNA+ (72%) subtypes during acclimation to seawater. [ABSTRACT FROM AUTHOR]

Abstract: We have studied intracellular pH (pHi) recovery in isolated trout gill mitochondrion-rich (MR) cells following acidification by the NH4Cl pre-pulse technique. Within a mixed MR cell population, one cell type displayed Na+-independent pHi recovery while the other cell type lacked a Na+-independent pHi recovery. Cells displaying Na+ independent recovery exhibited a significantly higher buffering capacity compared to cells lacking Na+-independent pHi recovery. Cells displaying Na+ independent recovery were identified as PNA+ (peanut lectin agluttinin binding) MR cells while those unable to recover were identified as PNA− (non-peanut lectin agluttinin binding) MR cells. Therefore, recovery from acidification in the absence of Na+ provides a direct functional marker for PNA+ and PNA− MR cells. Re-addition of Na+ to acidified cells resulted in a transient pHi recovery in both cell types. This event was abolished by amiloride (500µM) but it was insensitive to phenamil (50µM). The phorbol ester PMA (1µM) potentiated the Na+ induced pHi recovery suggesting that activation by PKC is required for continuous Na+/H+ exchanger activity in trout gill MR cells. This study is the first functional description of pHi recovery in lectin-identified trout gill MR cells and provides insight into a putative cellular signaling mechanism that may control pHi regulation in the gill epithelium. [Copyright &y& Elsevier]