The Caspian Sea as the greatest lake in the world has been faced with the different types of pollution. Among the different types of pollutants, petroleum (hydrocarbons) is one of the most important pollutants in the aquatic environment. Considering the economic and fisheries importance of the Caspian Sea, it is necessary to investigate the effect of such pollutant on valuable and endemic fish species. Since Caspian Kutum (Rutilus frisii) is a native and economic species of the Caspian Sea in the southern parts, the present study aimed to investigate the acute effects of water-soluble fraction of crude oil (WSF) on some physiological parameters of Caspian Kutum fingerlings at different times. Two experimental groups (WSF with LC50 of 0 and 50%) with three replicates for each one were considered in the experiment. Eighty fish (average weight of 0. 77 ± 0. 06 g) for each replicate were kept in an aquarium with the dimensions of 50 × 30 × 70 cm and exposed to WSF for 120 h. Then, 70 L WSF solution was added to each aquarium with the mentioned concentrations. Fifteen fish were sampled at 0 (before adding WSF), 6, 12, 24, 48, 72, 96 and 120 h after exposure to WSF for the measurement of lactate dehydrogenase activity and whole-body cortisol concentration. The results showed that the lactate dehydrogenase activity in fingerlings exposed to WSF (LC50=50%) was significantly higher than those kept in sea water (LC50=0%) during the sampling times (P<0. 05). There was a significant interaction between WSF concentration and time on the whole-body cortisol levels (P<0. 05). The results showed that crude oil had adverse effects on the physiology and welfare of Kutum fingerlings and the physiological responses were amplified in association with prolonged exposure to WSF.

A biosensor was developed for the detection of lactate dehydrogenase (LDH) enzyme using a lactate modified pencil graphite electrode (PGE). The sensor relies on the immobilization of the lactate on PGE, and LDH detection is based on the decrease of lactate peak current following oxidation to pyruvate in the presence of LDH. Square wave voltammetric technique was used for the assay of signals in the range of -0.6 to 0.8 V and a frequency of 25 Hz for the determination of LDH. The dependence of the response was investigated in terms of reaction time, washing time and LDH and NAD+amounts. Also, the electrochemical behavior of LDH treatment on the lactate modified PGE was studied. The electrode showed good selectivity, repeatability and an operational stability of about 90% of its original response for two weeks. Moreover, the sensor displayed a linear response range from 0.36- 2.13 U ml-1 for LDH with a detection limit of 0.16 U ml-1. The response time of the LDH-treated lactate modified PGE was found to be 2s. The relative standard deviation (RSD) obtained was 3.5% (for LDH 0.71 U ml-1 and n=3).

Background: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy that is associated with high morbidity and mortality. Salivary lactate dehydrogenase (LDH concentration), as an expression of cellular necrosis, may be a special marker of lesions that occur with changes in the integrity of the oral mucosa. This study was performed to determine the accuracy of salivary LDH as a clinical marker for HNSCC detection and to investigate the relationship between salivary LDH levels and tissue tumor detection. Methods: The case group consisted of 44 HNSCC patients and the control group consisted of 44 healthy subjects. The stage and grade of HNSCC were determined, and the LDH levels in collected saliva samples were measured in all subjects. The expression of LDH in tumors and healthy tissue margins was evaluated via immunohistochemistry. Results: The expression of LDH in the saliva of patients with HNSCC is significantly higher than that in the saliva of the healthy control group. The expression of salivary LDH in patients with oral squamous cell carcinoma (OSCC) is significantly higher than that in the other patients and healthy individuals in the control group. The levels of salivary LDH in patients with SCC of the tongue and lower oral cavity were significantly higher than those in other patients affected with SCC in other parts of the head and neck (P<0. 01). Conclusions: As this enzyme increases simultaneously in both tumoral tissues and saliva, it can serve as a useful diagnostic marker for the early diagnosis and prediction of HNSCC.