Recently, it was demonstrated that inbred strains of mice have a clearcut circadian rhythm of pineal and serum melatonin. Moreover, it is known that melatonin is involved in many immunoregulatory functions. Among them, hematopoiesis is influenced by the action of melatonin via melatonin-induced opioids on kappa-opioid receptors, which are present on stromal bone marrow cells. Therefore, the present study was carried out to investigate the presence of melatonin in the bone marrow in which immunocompetent cells are generated. Specifically, we aimed at answering the following question: are bone marrow cells involved in melatonin synthesis? In the present study, we demonstrate that (1) bone marrow cells contain high concentrations of melatonin; (2) bone marrow cells have a N-acetyltransferase activity and they express the mRNA encoding hydroxy-O-methyltransferase and (3) bone marrow cells cultured for a prolonged period exhibited high levels of melatonin. Results presented here suggest that mouse and human bone marrow and bone marrow cells are capable of de novo synthesis of melatonin, which may have intracellular and or paracrine functions.

Demand for organic milk is partially driven by consumer perceptions that it is more nutritious. However, there is still considerable uncertainty over whether the use of organic production standards affects milk quality. Here we report results of meta-analyses based on 170 published studies comparing the nutrient content of organic and conventional bovine milk. There were no significant differences in total SFA and MUFA concentrations between organic and conventional milk. However, concentrations of total PUFA and n-3 PUFA were significantly higher in organic milk, by an estimated 7 (95 % CI −1, 15) % and 56 (95 % CI 38, 74) %, respectively. Concentrations of α-linolenic acid (ALA), very long-chain n-3 fatty acids (EPA+DPA+DHA) and conjugated linoleic acid were also significantly higher in organic milk, by an 69 (95 % CI 53, 84) %, 57 (95 % CI 27, 87) % and 41 (95 % CI 14, 68) %, respectively. As there were no significant differences in total n-6 PUFA and linoleic acid (LA) concentrations, the n-6:n-3 and LA:ALA ratios were lower in organic milk, by an estimated 71 (95 % CI −122, −20) % and 93 (95 % CI −116, −70) %. It is concluded that organic bovine milk has a more desirable fatty acid composition than conventional milk. Meta-analyses also showed that organic milk has significantly higher α-tocopherol and Fe, but lower I and Se concentrations. Redundancy analysis of data from a large cross-European milk quality survey indicates that the higher grazing/conserved forage intakes in organic systems were the main reason for milk composition differences.

Demand for organic meat is partially driven by consumer perceptions that organic foods are more nutritious than non-organic foods. However, there have been no systematic reviews comparing specifically the nutrient content of organic and conventionally produced meat. In this study, we report results of a meta-analysis based on sixty-seven published studies comparing the composition of organic and non-organic meat products. For many nutritionally relevant compounds (e.g. minerals, antioxidants and most individual fatty acids (FA)), the evidence base was too weak for meaningful meta-analyses. However, significant differences in FA profiles were detected when data from all livestock species were pooled. Concentrations of SFA and MUFA were similar or slightly lower, respectively, in organic compared with conventional meat. Larger differences were detected for total PUFA and n-3 PUFA, which were an estimated 23 (95 % CI 11, 35) % and 47 (95 % CI 10, 84) % higher in organic meat, respectively. However, for these and many other composition parameters, for which meta-analyses found significant differences, heterogeneity was high, and this could be explained by differences between animal species/meat types. Evidence from controlled experimental studies indicates that the high grazing/forage-based diets prescribed under organic farming standards may be the main reason for differences in FA profiles. Further studies are required to enable meta-analyses for a wider range of parameters (e.g. antioxidant, vitamin and mineral concentrations) and to improve both precision and consistency of results for FA profiles for all species. Potential impacts of composition differences on human health are discussed.

The pineal gland is a vertebrate neuroendocrine organ converting environmental photoperiodic information into a biochemical message (melatonin) that subsequently regulates the activity of numerous target tissues after its release into the bloodstream. A phylogenetically conserved feature is increased melatonin synthesis during darkness, even though there are differences between mammals and birds in the regulation of rhythmic pinealocyte function. Membrane-bound melatonin receptors are found in many peripheral organs, including lymphoid glands and immune cells, from which melatonin receptor genes have been characterized and cloned. The expression of melatonin receptor genes within the immune system shows species and organ specificity. The pineal gland, via the rhythmical synthesis and release of melatonin, influences the development and function of the immune system, although the postreceptor signal transduction system is poorly understood. Circulating messages produced by activated immune cells are reciprocally perceived by the pineal gland and provide feedback for the regulation of pineal function. The pineal gland and the immune system are, therefore, reciprocally linked by bidirectional communication.

Very little is known about the effects of an organic or conventional diet on animal physiology and health. Here, we report the effect of contrasting crop protection (with or without chemosynthetic pesticides) and fertilization (manure or mineral fertilizers) regimes on feed composition and growth and the physiological parameters of rats. The use of manure instead of mineral fertilizers in feed production resulted in lower concentrations of protein (18.8 vs 20.6%) and cadmium (3.33 vs 4.92 μg/100 g) but higher concentrations of polyphenols (1.46 vs 0.89 g/100 g) in feeds and higher body protein (22.0 vs 21.5%), body ash (3.59 vs 3.51%), white blood cell count (10.86 vs 8.19 × 10³/mm³), plasma glucose (7.23 vs 6.22 mmol/L), leptin (3.56 vs 2.78 ng/mL), insulin-like growth factor 1 (1.87 vs 1.28 μg/mL), corticosterone (247 vs 209 ng/mL), and spontaneous lymphocyte proliferation (11.14 vs 5.03 × 10³ cpm) but lower plasma testosterone (1.07 vs 1.97 ng/mL) and mitogen stimulated proliferation of lymphocytes (182 vs 278 × 10³ cpm) in rats. There were no main effects of crop protection, but a range of significant interactions between fertilization and crop protection occurred.

The pineal hormone melatonin exhibits immunomodulatory activity well documented in mammals and birds. The mechanism of melatonin action within the immune system is, however, poorly understood. In mammalian immune cells in vitro, melatonin acts mainly as an antiapoptotic, oncostatic and antiproliferative agent, and these effects are exerted via specific receptors or are related to its free radical scavenging activity. In previous studies we have found that in short-term chicken splenocyte cultures in vitro melatonin stimulated basil proliferation and inhibited that stimulated with phytohemagglutinin, a T-cell mitogen. This paper is devoted to the involvement of membrane receptors, previously characterised by us as MT2 (Mel(1b)) and Mel(1c) subtypes, in the above mentioned melatonin effects in chicken splenocyte cultures. For this purpose, in present study a nonselective melatonin receptor antagonist, luzindole, and the selective MT2 blocker, 4P-PDOT, were used. The effect of melatonin on second messengers, cyclic adenosine-3',5'-monophosphate (cAMP) and inositol-1,4,5-trisphosphate (IP(3)), involved in the regulation of proliferation, was examined. We have found that the stimulation of proliferation occurs via Mel(1c) receptor and is associated with the changes in intracellular second messengers concentration: a decrease in cAMP and an increase in IP(3). In contrast, in mitogen-activated splenocytes, melatonin-induced inhibition of proliferation is mediated by MT2 receptors and is related to cAMP accumulation, as well as a decrease in IP(3). In conclusion, we have demonstrated that the stimulatory and inhibitory effect of melatonin on chicken splenocytes in vitro, dependent on the magnitude of cell stimulation, resulted from two different subtypes of membrane receptors.

This study examined the effect of melatonin (MLT) on in vitro phagocytosis of testicular macrophages taken from control and streptozotocin (STZ)-induced diabetic rats and the possible mechanism of its action. The phagocytic activity was measured as a number of latex beads ingested by 100 macrophages (PI, phagocytic index) in consecutive time points of the incubation. Changes in intracellular free calcium level [Ca2+]i in isolated macrophages in vitro were measured with the use of ratio-image fluorescence microscopy (fluorescent dye: Fura2/AM). Phagocytic index in macrophages isolated from healthy rats was 20% higher than in those from diabetic animals. Melatonin in physiological concentration (10(-7) M) significantly (p < 0.05) increased the PI in testicular macrophages from control animals (PI = 68 +/- 5 with MLT compared to PI = 46 +/- 7 without MLT) while no such effect was observed in the cells from diabetic rats (PI = 36 +/- 23 with MLT compared to PI = 31 +/- 11 without MLT). Basal [Ca2+]i was significantly (p < 0.01) higher in macrophages from diabetic rats compared to control. Stimulation of both control and diabetic testicular macrophages with 10(-7) M MLT resulted in a significant (p < 0.05) increase in [Ca2+]i in cells incubated in 2.5 mM calcium solution while no such response was observed in calcium-free Tyrode solution. However, MLT evoked [Ca2+]i response in macrophages isolated from diabetic animals was much lower than in macrophages isolated from age-matched controls and the time needed for maximal response was much longer. Lack of response in calcium-free solution suggests that extracellular calcium may be necessary to trigger MLT response and in its progression.

The immunomodulatory action of melatonin in different animal species is already well known, although the mechanism(s) by which the indoleamine influences the immune system have yet to be fully elucidated. Previously, we have shown both anti-inflammatory and opioid-mediated influence of exogenous melatonin on thioglycollate-induced peritonitis in young chickens. In the present study, the kinetics of peritonitis and splenocyte proliferation were compared in chickens reared in both seasons under the same L:D 12:12 conditions. These two aspects of the immune response were correlated with the diurnal rhythm of pineal gland function, measured by the activity of N-acetyltransferase (NAT), a key enzyme in melatonin biosynthesis. The results revealed seasonal changes in the circadian rhythm of pineal NAT activity occurring in parallel to the natural local geophysical seasons. These changes appeared to influence the development of peritonitis and splenocyte responsiveness to mitogenic stimulation in vitro. Moreover, the existence of bidirectional communication between the pineal gland and the activated immune system was supported by the decreased activity of pineal NAT in chickens with peritonitis compared with control birds.