Photoperiodic manipulation modulates the innate and cell mediated immune functions in the fresh water snake, Natrix piscator

Annual rhythm in immune functions of blood leucocytes in an ophidian, Natrix piscator

Annual variations in animal's physiological functions are an essential strategy to deal with seasonal challenges which also vary according to the time of year. Information regarding annual adaptations in the immune-competence to cope with seasonal stressors in reptiles is scarce. The present research plan was designed to analyze the presence of circannual immune rhythms in defense responses of the leucocytes in an ophidian, Natrix piscator. Peripheral blood leucocytes were obtained, counted, and superoxide anion production, neutrophil phagocytosis, and nitrite release were tested to assess the innate immune functions. Peripheral blood lymphocytes were separated by centrifugation (utilizing density gradient) and the cell proliferation was measured. The Cosinor rhythmometry disclosed the presence of significant annual rhythms in the number of leucocytes, superoxide anion production, nitric oxide production, and proliferation of stimulated lymphocytes. The authors found that respiratory burst activity and proliferative responses of lymphocytes were crucial immune responses that showed the annual rhythm. It was summarized that the immune function of the N. piscator is a labile attribute that makes the animal competent to cope with the seasonal stressor by adjustment in the potency of response.

Past, Present, and Future of Naturally Occurring Antimicrobials Related to Snake Venoms

This review focuses on proteins and peptides with antimicrobial activity because these biopolymers can be useful in the fight against infectious diseases and to overcome the critical problem of microbial resistance to antibiotics. In fact, snakes show the highest diversification among reptiles, surviving in various environments; their innate immunity is similar to mammals and the response of their plasma to bacteria and fungi has been explored mainly in ecological studies. Snake venoms are a rich source of components that have a variety of biological functions. Among them are proteins like lectins, metalloproteinases, serine proteinases, L-amino acid oxidases, phospholipases type A₂, cysteine-rich secretory proteins, as well as many oligopeptides, such as waprins, cardiotoxins, cathelicidins, and β-defensins. In vitro, these biomolecules were shown to be active against bacteria, fungi, parasites, and viruses that are pathogenic to humans. Not only cathelicidins, but all other proteins and oligopeptides from snake venom have been proteolyzed to provide short antimicrobial peptides, or for use as templates for developing a variety of short unnatural sequences based on their structures. In addition to organizing and discussing an expressive amount of information, this review also describes new β-defensin sequences of Sistrurus miliarius that can lead to novel peptide-based antimicrobial agents, using a multidisciplinary approach that includes sequence phylogeny.

Melatonin as a Possible Natural Anti-Viral Compound in Plant Biocontrol

Melatonin is a multifunctional and ubiquitous molecule. In animals, melatonin is a hormone that is involved in a wide range of physiological activities and is also an excellent antioxidant. In plants, it has been considered a master regulator of multiple physiological processes as well as of hormonal homeostasis. Likewise, it is known for its role as a protective biomolecule and activator of tolerance and resistance against biotic and abiotic stress in plants. Since infections by pathogens such as bacteria, fungi and viruses in crops result in large economic losses, interest has been aroused in determining whether melatonin plays a relevant role in plant defense systems against pathogens in general, and against viruses in particular. Currently, several strategies have been applied to combat infection by pathogens, one of them is the use of eco-friendly chemical compounds that induce systemic resistance. Few studies have addressed the use of melatonin as a biocontrol agent for plant diseases caused by viruses. Exogenous melatonin treatments have been used to reduce the incidence of several virus diseases, reducing symptoms, virus titer, and even eradicating the proliferation of viruses such as Tobacco Mosaic Virus, Apple Stem Grooving Virus, Rice Stripe Virus and Alfalfa Mosaic Virus in tomato, apple, rice and eggplant, respectively. The possibilities of using melatonin as a possible natural virus biocontrol agent are discussed.

Photoperiodic regulation of the splenocyte immune responses in the fresh water snake, Natrixpiscator

Photoperiod and melatonin are important regulators of immunity. We hypothesized that these two factors play an important role in the regulation of immune responses in the Natrix piscator. Animals were kept in either short or long days and splenocyte immune responses were studied. Respiratory burst activity of splenocytes was assessed through reduction of nitrobluetetrazolium salt while production of nitric oxide was assessed indirectly by nitrite assay. Density gradient centrifugation was used to isolate splenic lymphocytes which were utilized to study proliferation with and without mitogens. Super oxide production by splenocytes was reduced significantly in the cultures obtained from animals kept either in short or long days. Nitrite release was decreased when animals were subjected to long days. The photoperiodic alterations acted differentially on proliferations of the splenic lymphocytes. Spontaneous and mitogen-induced proliferation of splenic lymphocytes were enhanced in cultures obtained from snakes maintained in short days when compared with cultures from snakes obtained either from long day or natural day length conditions. In vitro melatonin significantly enhanced the splenic lymphocyte proliferation of the cultures obtained from animals kept in long days when compared with splenic lymphocyte proliferations of the cultures obtained from long day animals or the animals kept in natural day length conditions. We found evidence which suggest that photoperiod may influence seasonal energy budgets and induce adjustments which optimize energy allocation for costly physiological processes such as immune function. In seasonally breeding animals such as Natrix piscator, the pineal hormone melatonin assists in the suppression of reproduction and elevation of immunity, which are the crucial adaptation for perpetuation of species.