ABSTRACT Introduction: Hypokalemia is a frequent hydroelectrolytic disorder, associated with systemic and multifactorial diseases, whose acute form can be complicated and cause death, but in its chronic presentation it can be a marker of nephropathy. Objective: To characterize the profile of the patient with non-drug hypokalemia seen in an emergency. Methods: The records of patients older than 18 years diagnosed with hypokalemia, admitted to the hospital from June 2018 to December 2019, were reviewed. Demographic data, medical history, and post-treatment evolution were collected. It was compared with 108 patients without hypokalemia seen in the same period. Results: 87 cases with mean age of 38.5 years were studied. 90.8% were men under 50 years of age, who worked as farmers (29.9%), with history of exposure to pesticides and high ambient temperatures. Most of them had no history of previous cardiometabolic or renal disease. 48.3% of all patients with hypokalemia (n = 42) had creatinine higher than 1.2 mg/dL and 63% had hyponatremia. Hypokalemia was moderate in 39% and severe in 12%, and it was found that men were affected 4.7 times more than women. Regarding the group without hypokalemia and abnormal creatinine, they had higher frequency of chronic disease (92.5% versus 8%). Conclusions: Non-drug hypokalemia was found in male farmers, without chronic disease, but with evidence of early nephropathy and hyponatremia. The possibility of Mesoamerican nephropathy was suggested. A regional epidemiological alert and a prevention and control program should be established.

RESUMEN Introducción: La hipopotasemia es un trastorno hidroelectrolítico frecuente, asociado a enfermedades sistémicas y multifactoriales, cuya forma aguda puede complicarse y causar la muerte, pero en su presentación crónica puede ser un marcador de nefropatía. Objetivo: Caracterizar el perfil del paciente con hipopotasemia no medicamentosa atendidos de emergencia. Métodos: Se revisaron los registros de pacientes mayores de 18 años con diagnóstico de hipopotasemia, ingresados en el hospital en el período de junio 2018 a diciembre de 2019. Se colectaron datos demográficos, antecedentes médicos y evolución postratamiento. Se comparó con 108 pacientes sin hipopotasemia atendidos en el período de estudio. Resultados: Se encontraron 87 casos con edad media de 38,5 años. El 90,8 % eran hombres menores de 50 años, de oficio agricultor (29,9 %), con historia de exposición a plaguicidas y a altas temperaturas ambientales. La mayoría de ellos no tenía historia de enfermedad cardiometabólicas o renal previa. El 48,3 % de todos los pacientes con hipopotasemia (n = 42) tenía creatinina mayor a 1,2 mg/dL y 63 % tenía hiponatremia. La hipopotasemia fue moderada en 39 % y severa en 12 %, los hombres 4,7 veces más afectados que las mujeres. Respecto al grupo sin hipopotasemia y creatinina anormal, tenían mayor frecuencia de enfermedad crónica (92,5 % versus 8 %). Conclusiones: Se encontró hipopotasemia no medicamentosa en varones agricultores, sin enfermedad crónica, pero con datos de nefropatía temprana e hiponatremia, se sugirió la posibilidad de nefropatía mesoamericana. Debe establecerse una alerta epidemiológica regional y un programa de prevención y control.

ABSTRACT. This work aimed to improve reproductive maturation in two penaeoid species (Artemesia longinaris and Pleoticus muelleri) by using carotenes added in artificial feeds and comparing antioxidant activity and carotenoids profiles. Immature females were kept for 45 days at salinity 33, temperature at 18°C, pH 7, 12:12 h photoperiod, ammonium <0.2mg L−1 and seawater exchanged at 100% per day. Feeding regimes consisted of 50% fresh frozen ingredients (clam muscle and squid mantle) and 50% dry pellets. For each species, three pelletized feeds were tested, one as a control (C) and two supplemented each one with 300 mg astaxanthin (A) and β-carotene (B) kg−1 of diet. At the end of the trials, ovaries, midgut gland, and integument were sampled. In both species, the addition of carotenoids improved ovarian development: 100% of females fed A or B diets were mature, but of the females fed with diet C only 75% (P. muelleri) and 64% (A. longinaris) matured. Ovaries of mature females exhibited the highest concentration of carotenoids. The abundance of free astaxanthin regarding total carotenes, suggests that excess of free astaxanthin could be biotransformed to esterified astaxanthin. The scavenging properties were evaluated against the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical by electron resonance spectroscopy (EPR). For all feed treatments, the extracts exhibited strong DPPH scavenging activity, without significant differences among them.

Water-soluble extracts from seaweeds Macrocystis pyrifera (M) and Undaria pinnatifida (U) were prepared to use the polysaccharide bioactive fraction as functional food. Chemical analysis showed that the main components of both extracts were mannitol and fucoidans. Also in both cases minor amounts of rhamnose, glucose, xylose and arabinose were determine. Content of fucose+galactose was higher in U. pinnatifida (8.7%) than in M. pyrifera (5.9%). Extracts were used as feed additive to Artemesia longinaris at inclusion levels of 1 and 2% (M1 and M2; U1 and U2), a diet without extract was used as control. Radical scavenging activities were estimated for two extracts and for midgut gland samples of experimental animals. Scavenging activity was detected in both extracts, the signal decayed to 50 and 62% in 18 min for U. pinnatifida and M. pyrifera, respectively. After 30 days of feeding, results did not show variation of survival, but growth was improved in animals fed with U1 and U2. Supplementation with 1 and 2% of U. pinnatifida showed similar quenching capacity of homogenates than those fed with M2 with a rapid 1,1-diphenylpicrylhydrazyl (DPPH) decay at 2 min of reaction. Recommended concentration for culture A. longinaris is 2%, as it is that produce the best antioxidant capacity, although the growth performance was improved also significantly only with U. pinnatifida extract.

The aim of the present study was to determine lethal and sublethal effects of nitrite on the freshwater prawn, Palaemonetes argentinus (Nobili 1901). The 24, 48, 72 and 96 h median lethal concentration (LC50) of nitrite were found to be 103.07; 91.94; 82.39 and 62.53 mg L-1, respectively. The antioxidant activity of superoxide dismutase (SOD) was positively correlated with the concentration of nitrite in the environment, thus increasing the formation of hydrogen peroxide, substrate of catalase (CAT), which also showed an increased activity under the same experimental conditions. Histological samples showed that nitrite exposure caused hyperplasia, necrosis and changes in the lamellar epithelium in gills; while the effects in the hepatopancreas were degenerative desquamation, epithelial deterioration and hyperplasia. In conclusion, nitrite toxicity in P. argentinus increases with time of exposure. Moreover, this study proves that histological analysis of crustacean gills and/or hepatopancreas is a useful tool to determine the presence of toxic concentrations of nitrite in the water. Additionally, the measurement of the activity of antioxidant enzymes (e.g., SOD and CAT) as possible indicators of nitrite pollution should be considered in future studies.

El objetivo del presente estudio fue determinar los efectos letales y subletales del nitrito en el camarón de agua dulce, Palaemonetes argentinus (Nobili 1901). Las concentraciones letales medias (LC50) de nitrito a las 24; 48; 72 y 96 h al nitrito fueron 103,07; 91,94; 82,39 y 62,53 mg L-1, respectivamente. La actividad antioxidante de la superóxido dismutasa (SOD) se correlacionó positivamente con la concentración de nitrito ambiental; este incremento en su actividad eleva la formación de peróxido de hidrógeno, sustrato de la catalasa (CAT), que también mostró un incremento en su actividad bajo las mismas condiciones experimentales. Las muestras histológicas evidenciaron que la exposición al nitrito causa hiperplasia, necrosis y cambios en el epitelio lamelar en las branquias; mientras que en el hepatopancreas los efectos son descamación degenerativa, deterioro epitelial e hiperplasia. En conclusión, la toxicidad del nitrito en P. argentinus se incrementa conforme el tiempo de exposición. Este estudio demuestra que el análisis histológico de las branquias y/o hepatopancreas del camarón P. argentinus es útil para determinar la presencia de concentraciones tóxicas de nitrito en el agua. Además, la medición de las enzimas antioxidantes (por ejemplo, SOD y CAT) debería ser considerado en futuros estudios como posibles indicadores de contaminación por nitrito.

The present study compared the effect of different starch/cellulose ratios (30/0, 20/10, 10/20, 0/30) on the metabolic response and apparent digestibility in two species of penaeoids: Artemesia longinaris and Pleoticus muelleri. Adult animals were used in order to obtain sufficient quantities of haemolymph and faecal material for analysis. No significant differences were found in levels of plasma metabolites in P. muelleri, but in A. longinaris, a significant increase was observed in glucose, total protein, and cholesterol in correlation with increased dietary starch. The apparent digestibility coefficients decreased from 83.7% to 51.2% (A. longinaris) and from 71.9% to 7.6% (P. muelleri) as the dietary starch levels increased. The ratio of amylase activity to protease activity (A/P ratio) declined in A. longinaris when the percentage of dietary starch increased. In contrast, the A/P ratio for P. muelleri increased with higher starch concentrations. These results demonstrated a close relationship between the feeding habits and digestive physiology of the two species studied; they also suggest a more herbivorous behavior for A. longinaris and more omnivorous habits for P. muelleri.

En el presente estudio se comparó el efecto de diferentes concentraciones de almidón/celulosa (30/0; 20/10; 10/20; 0/30) sobre la respuesta metabólica y la digestibilidad aparente en dos especies de peneidos, Artemesia longinaris y Pleoticus muelleri. Se utilizaron animales adultos a fin de obtener cantidades suficientes de hemolinfa y heces para los análisis. No hubo diferencias significativas en los niveles de metabolitos plasmáticos en P. muelleri, en cambio en A. longinaris se observó un incremento significativo de la glucosa, proteínas totales y colesterol en relación con el aumento del almidón en la dieta. Los coeficientes de digestibilidad aparente disminuyeron de 83,7% a 51,2% (A. longinaris) y de 71,9% a 7,6% (P. muelleri) a medida que los porcentajes de almidón en la dieta aumentaron. El cociente entre la actividad de amilasa y proteasa (A/P) se redujo en A. longinaris con los mayores porcentajes de almidón dietario; por el contrario, el cociente A/P en P. muelleri aumentó cuando la concentración fue más alta. Estos resultados demostraron que existe una estrecha relación entre los hábitos alimentarios y la fisiología digestiva de las dos especies estudiadas; sugiriendo un comportamiento más herbívoro para A. longinaris y más omnívoro para P. muelleri.

The present work describes the effect of different salinities on the functional morphology of the P. argentinus hepatopancreas and analyses the tissue recovery after re-acclimation to freshwater. Adult prawns of both sexes at sexual rest were collected from a tributary of the Mar Chiquita coastal lagoon. The prawns were acclimated in aquaria to four salinity conditions: 0 (control), 8, 16 and 24‰. To evaluate the possible tissular recovery, after 60 days individuals from all the treatments were gradually acclimated to freshwater and maintained for other 30 days. Hepatopancreas samples were processed at the beginning of the trial and every 30 days using standard histological techniques for OM and TEM. The individuals from all the treatments, except the controls, showed a continuous weight decrease, and survival was lower when higher the salinity. At 30 days from the beginning of the experiment, hepatopancreas from 16 and 24‰ salinities showed an enlarged tubular lumen and an infolded basal lamina. Ultratructurally, nuclear retraction, cytoplasmolysis, and RER membranes separated with electron-dense content were observed in all the treatments except 0‰. After 60 days, profound alterations were observed with the three treatments. After the re-acclimation period, there was no reestablishment of the functional cytology. The tolerance to short-term salinity changes explains the capability of this prawn to inhabit in estuarine environments.

O objetivo do presente trabalho foi determinar a digestibilidade aparente in vivo da proteína bruta de ingredientes de origem animal (farinhas de peixe, osso e carne e concentrado de proteína de lula) e ingredientes vegetais (farinha de soja) em camarões Artemesia longinaris utilizando rações contendo 0,25% de óxido de cromo. Três grupos de camarões, utilizados como replicatas, foram alimentados e as fezes coletadas. A velocidade de hidrólise da proteína de cada ração foi medida in vitro utilizando extrato enzimático da glândula do intestino médio dos camarões alimentados com a ração correspondente e foi comparado com aqueles obtidos com o extrato enzimático de camarões selvagens. Os coeficientes de digestibilidade aparente in vivo mostraram diferenças significativas entre as rações testadas (P<0,05). A farinha de peixe apresentou a maior digestibilidade (92%), enquanto valores intermediários de digestibilidade (83%) foram encontrados para a farinha de carne e ossos. A ração contendo farinha de soja e concentrado de proteína de lula resultou em menor digestibilidade (63%). Não houve diferença significativa entre os valores de digestibilidade in vitro para as rações testadas. Estes resultados indicam a limitação inerente dos ensaios enzimáticos in vitro, os quais poderiam ser complementados com estudos in vivo.

This study was undertaken to determine the in vivo crude protein apparent digestibility in the prawn Artemesia longinaris, using feeds with 0.25% of chromic oxide and animal (fish meal, meat and bone meal and squid protein concentrate) and plant (soybean meal) ingredients. Three replicate groups of prawn were fed and the feces were collected. The rate of protein hydrolysis was measured in vitro using midgut gland enzyme extract from the prawns fed the respective feeds and was compared with those found with enzyme extract of wild prawn. The in vivo apparent digestibility coefficients showed significant differences among the feeds (P<0.05). Fish meal feed presented the highest digestibility (92%); intermediate digestibility (83%) was found for meat and bone meal feed, and the less digestible feed (63%) was that containing soybean meal and squid proteins concentrate. No significant differences in the in vitro protein digestibility were found among the experimental feeds. The results indicated the limitation of in vitro enzyme assays and that it should be complemented by in vivo studies.

Growth, survival and molting rate in Palaemonetes argentinus Nobili, 1901 were compared under different light-dark conditions. During 80 days, 150 immatures of both sexes (initial mean weight 0.09±0.002g), from Los Padres lagoon, Mar del Plata, Argentina, were maintained in aquaria at 19±0.4°C under three light conditions: 0:24, 10:14 and 13:11 (L-D). They were fed daily on an artificial diet (45% proteins, 17.2% lipids, 7% water, 7% ash). Good weight increment was obtained with the three treatments, finding a positive linear correlation between mean weight and time (0:24, r=0.97; 10:14, r=0.99; 13:11, r=0.98). There were no significant differences in the percentage increment in mean weight among the treatments (0:24, 19.3%; 10:14, 29.3% and 13:11, 26.5%) (p<0.05). Molting rate was significantly higher at a long-day photoperiod (MR=1.7) than at a short-day (MR=0.6) or continuous dark condition (MR=0.3) (p<0.05). The lowest survival was found in animals maintained under 13:11 L-D conditions (77%), being statistically different of the other two treatments (92% and 89% at 10:14 and 0:24, respectively) (p<0.05). These results suggest that the best growth and survival in P. argentinus result with a 10:14 L-D cycle, and that the growth is less affected by photoperiod than molting rate and survival.

The relationship between the molting cycle and gonadal maturation was investigated in the Pleoticus muelleri population from coastal waters of Mar del Plata, Argentina. The analysis of the molting activity revealed activity patterns that vary conspicuously with both the changes in shrimp reproductive status and the season. Males and females exhibited a molt synchronism and the intermolt lengthened during the reproductive season. Intermolt and early premolt females presented ripe ovaries, but in late premolt females, ovaries were in resorbed condition. The reproductive activity begins in spring and extends until autumn, with the maximum of impregnated females in summer. Ovarian development from immature to ripe was rapid in spring and summer, probably due to the increase in temperature and photophase. The potentiality of impregnation is independent of the size of females at least 6 g in weight. The large quantity of reserves and food needed for oocyte development was evidenced by the increment of the gonadosomatic index during maturation. Females showed higher hepatopancreatic indexes than males, which could be related to the high energetic requirement.

El objetivo del trabajo fue estudiar el ciclo de muda de la población de Pleoticus muelleri de Mar del Plata mediante el análisis de la proporción de estadios de muda y su relación con la madurez gonadal. El análisis del ciclo de muda reveló patrones de actividad que se relacionan con el estadio reproductor y con la estación del año. Machos y hembras exhibieron sincronía en la muda. Durante el pico de la estación reproductora, el verano, se prolonga la duración de la intermuda. Las hembras maduras detienen el ciclo de muda en la intemuda o inicio de la premuda y sólo lo reanudan después del desove; en premuda avanzada los ovarios están en reabsorción. La actividad reproductora se inicia en la primavera y se extiende hasta el otoño, con el máximo de hembras impregnadas en verano. Los ovarios tienen crecimiento rápido, desde inmaduros hasta maduración total, desde la primavera hasta el verano, como respuesta al incremento de la temperatura y del fotoperíodo. La potencialidad de impregnación en las hembras es independiente de la talla; la talla inicial corresponde a los 6 g de peso. El incremento del índice gonadosomático durante la maduración indica la gran cantidad de reservas que requiere el desarrollo ovocitario. Este requerimiento se evidencia por los valores de los índices hepatopancreáticos de las hembras que fueron más altos que los de los machos.

Este trabalho teve como objetivo comparar o grau de desenvolvimento ovariano de remeas ablacionadas e intactas de Pleoticus muelleri e avaliar a influência da ablação sobre a freqüência da muda. As femeas, de 7 a 22 g de peso, foram mantidas em condições de cultivo com fotoperíodo de 12:12, temperatura entre 15 e 17ºC, salinidade de 31 e alimentadas com lula, camarão e bivalvos frescos. Foram pesados e fixados os ovários e hepatopâncreas, realizando um controle histológico nos 4; 9; 15; 20; 40 e 50 dias. O índice gonadossomático variou entre 0,925 e 3,747 (controle) e entre 1,457 e 5,035 (ablacionados). Determinou-se valores de índice hepatopancreático entre 2,059 a 4,520 (controle) e de 3,471 a 4,471 (ablacionados). A duração média da intermuda foi 21,7 :j: 3,9 e 23,2 :j: 2,4 dias para o grupo controle e ablacionados, respectivamente. Ao finalizar o experimento a análise histológica demostrou que os ovários das femeas ablacionadas encontravam-se totalmente amadurecidos e os do controle em vitelogênese primária. Conclui-se que a ablação peduncular acelera a maturação ovariana de P. muelleri, sem modificar a freqüência da muda. O índice ovariano é independente do tamanho no intervalo de peso estudado e a ablação não apresentou efeito sobre o peso relativo dos hepatopâncreas.

The objective of this study was to compare the ovary development of ablated and non-ablated females of Pleoticus muelleri and to evaluate the influence of eyestalk ablation on molting frequency. The females (7-22 g weight) were maintained under culture conditions with 12: 12 fotoperiod, 15-17ºC temperature and 31%0 salinity. They were fed on fresh squid, prawn and clam. The ovaries and digestive glands were weighed and fixed for histological examination at 4,9, 15,20, 40, and 50 days. Gonad index varied between 0.925 and 3.747 (control) and 1.457 and 5.035 (ablated). The digestive gland index ranged from 2.059 to 4.520 (control) and 3.471 to 4.471 (ablated). The intermolt duration was 21.7 :j: 3.9 and 23.2 :j: 2.4 for the control and ablated respectively. At the end of the experiment the ovaries of ablated females were mature and those of the control were in primary vitellogenesis. It was concluded that the eyestalk ablation in P. muelleri resulted in precocious maturation of the ovary without changes in the molting frequency. The ovary index was size-independent. Ablation had no effect on the relative weight of digestive gland.