جستجوی مقالات مرتبط با کلیدواژه "ultrastructure" در نشریات گروه "شیلات"

Marine nematodes are the most important sediment living invertebrates. Free living nematodes are considered as bio indicators in coastal areas. Many pollutants such as polychlorinated biphenyls may affect their physiological process. The present study is conducted to describe physiological and histological pattern of marine nematode (Oncholaimus campylocercoides) from north Persian Gulf. Three locations with different concentrations of PCBs were selected in Bandar Abbas for sampling. Sex steroid hormones (progesterone, testosterone and 17-B estradiol) were analysed after separation and purification of marine nematodes from sediments. Moreover, fine structures of ovocyte and spermatozoa were studied after histological observation. Results showed that sex ratios were F(1): M(0.97), F(1): M (0.9), F(1): M(0.5) in locations with 0.01, 0.02 and 0.1 µg/mL tissue PCB concentrations, respectively. Level of 17 β-estradiol (1.2±0.07pg/mL) in females at the location with 0.1 µg/mL PCB (power plant) was significantly higher than that in other two sampling locations. Also high level of testosterone (0.4±0.07 pg/mL) was observed in males and females at the polluted sampling site compared with that in other two locations. Histological study showed that in the location with high PCBs, there was an obvious increase in size of oocytes. We concluded that PCBs can affect sex steroid changes as endocride disruptors in Oncholaimus campylocercoides. Results of this study supported findings of previous studies on PCB endocrine disrupting roles in marine organisms.

Alkaline pH is one of the most important problems of our aquatic habitat. We used Stigonematalean native cyanobacterium Fischerella sp. FS 18 as our model strain, andstudied it under different alkaline pHs (7, 9 and rarely 11) under two different – short and long- time treatments (24 and 96 hours after inoculation). Spectroscopic results showed that both alkalinity and time affected growth rate, phycobilisome and chlorophyll production. Response surface plot analysis of distribution showed that the pH borders between 8.5 to  9 would be critical at 24 hours after inoculation reaching to the highest rates of phycobilisomes. Spectrofluorimetric analysis showed that the highest photosystem I/ photosystem II may be seen at 24 hours at pH9. Photosynthesis- Irradiance curves showed that the highest rate of maximum photosynthesis belonged to pH9 in the short time treatment (24 hours). Increasing the time (96 hours) decreased the maximum amount of oxygen liberation significantly. Moving from the optimum conditions (even slightly) caused a sharp decline in the amount of alpha. The slope of decline was steep until near neutral and longtime condition.  Decreasing the time, and at the same time increasing alkalinity (alkaline pH) caused higher activity of photosystems especially photosystem I which lead to higher reductant production and cyclic electron flow operation. Distinct borders of pH (8.5-9) at 24 hours caused considerably high growth and matter production. This was naturally true for phycocyanin, phycoerythrin and the other economically important matters.

The aim of this study was to investigate the structure and ultrastructure of the digestive tract of Qinling lenok (Brachymystax tsinlingensis Li, 1966), a cold water Salmonidae fish, an endangered teleost species, with high potential for controlled rearing in Shaanxi Province of China, by light and electron microscopy. Morphological data of the digestive tract are important for understanding fish nutrition, pathological or physiological alterations. The histological structure of Qinling lenok consists of four layers: mucosa, submucosa, muscularis and serosa. Taste buds were found in lips and esophagus. The esophageal mucosa consists of undifferentiated mucous cells and surface epithelial cells. The U-shaped stomach was divided into cardiac, fundic and pyloric region. There are numerous gastric glands in the submucosa layer of the cardiac and fundic stomach, but none of them are present in the pyloric region. The convoluted tube-shape intestine is lined by simple columnar epithelial cells with microvilli at the apical surface, with an intestinal coefficient of 0.61. There are numerous goblet cells in the intestine. Finger-like pyloric caeca were found in the front of intestine tube, with number ranged from 42 to 88. In ultrastructural level, mucous and glandular cells in the stomach were found, the glandular cell with well-developed tubulovesicular system, a great amount of pepsinogen granules, mitochondria and Golgi apparatus. The enterocytes with abundant microvilli contained mitochondria and lysosome, and mucous granules of goblet cells were apparent in the intestine. High density of lipid droplets of pyloric caeca might be concerned with fat-absorption. The present study suggests that the digestive tract of Qinling lenok is similar to other carnivorous fishes, in relation to its feeding habits.

In this study, we explored the pathogenic effects of white spot syndrome virus (WSSV) and effects of yeast cell wall in the red claw crayfish, Cherax quadricarinatus, by investigating the activity of enzymes related to innate immune function following artificial infection of immunized and non-immunized crayfish. Our results reveal that the activity of four enzymes, phenoloxidase (PO), peroxidase (POD), superoxide dismutase (SOD) and lysozyme (LSZ), increased in the hepatopancreas and antennal gland of C. quadricarinatus 6 – 24 hours after exposure to WSSV. Activity levels of these enzymes decreased rapidly, so that 72 h post-exposure the activity of the enzymes in WSSV-infected crayfish were significantly lower than those of the control individuals (except for LSZ). Interestingly, we found that immunization with yeast cell wall before challenge with WSSV conferred an immune protection rate of 51.86% at 7 days post-infection, demonstrating that yeast cell wall could improve immune-related enzyme activity in the crayfish and enhance the anti-viral defenses of this species. Morphological examination by transmission electron microscopy revealed significant damage in the hepatopancreas and antennal glands of infected crayfish. WSSV infection caused damage to the epithelium of the hepatopancreas and antennas and reduced the number and size of microvilli. In addition, mitochondria morphology changed following infection, with parts of the cristae diminishing leaving large vacuoles. Moreover, the dictyosome morphology changed, the lysosome membranes ruptured, and heterochromatinized nuclei could be seen in cells with ruptured nuclear membranes although no WSSV particles appeared in the hepatopancreas or in the antennal gland.

The present study was conducted to evaluate the effect of 20 d starvation on growth, survival, histomorphology and ultrastructure changes in the digestive system of juvenile red swamp crayfish (Procambarus clarkii). Juveniles were divided into two groups: a food-deprived group and a control group at 9 day after hatch (DAH). Individuals were sampled at 14, 20, 29 DAH. During the 20 d fasting period, the mean body weight and total body length of crayfish fluctuated around 10.17 mg and 8.12mm respectively, and the mortality was zero. Histomorphological changes of digestive system were observed in the food-deprived group after 20 days of starvation: the esophagus and stomach walls were thinning, the epithelium atrophied to cuboidal, nuclei were darker and smaller, and nucleolus was difficult to observe; the midgut and hindgut showed wider volume, thinning wall, atrophied epithelial and muscularis and shorter ridges; and hepatopancreas tubule lumens were wider, the lipid droplets in R-cells were smaller and less, and the quantity of typical B-cells decreased. Changes in the ultrastructure of starved crayfish were also observed: the mitochondria of midgut epithelium and R-cells were swollen and vacuolated, and the ridges of which were fractured and reduced. In addition, the electron density of cytoplasmic matrix of R-cells decreased, and the quantity of glycogen granules and lipids also decreased. Changes in the ultrastructure of B-cells were similar to those of R-cells. Though degeneration in histological structure and function of digestive organs were obvious during starvation, juvenile P. clarkii was able to endure a relative long-term starvation.

Viral pathogens are major causes of outbreaks in shrimp farms throughout the world. Monodon baculovirus has been known to be invasive in 85-100% of the shrimp hatcheries, in early or late stages of shrimp. Three-hundred and sixty juvenile of Litopenaeus vannamei with average (±SD) size of 7.99±0.54 g and 3600 post larvae 10-15 were prepared from Shrimp Research Station located in Helleh and 3 hatcheries from Bushehr Province, southern part of Iran, respectively. They were allocated to 9 glass aquariums (50×50×60cm) as 2 groups (postlarvae and juvenile), controls with 3 replications using100 liters well aerated water. They were exposed to MBV as water-born path. Concerning the pathogenesis, three phases were observed. The quantity of intranuclear occlusion bodies was 1-9. Mortality was only observed in postlarvae but not in adult or control groups. It is concluded that MBV can be an invasive pathogen for SPF offspring or postlarvae of L. vannamei being imported to Iran.