Seed priming: state of the art and new perspectives.

Priming applied to commercial seed lots is widely used by seed technologists to enhance seed vigour in terms of germination potential and increased stress tolerance. Priming can be also valuable to seed bank operators who need improved protocols of ex situ conservation of germplasm collections (crop and native species). Depending on plant species, seed morphology and physiology, different priming treatments can be applied, all of them triggering the so-called 'pre-germinative metabolism'. This physiological process takes place during early seed imbibition and includes the seed repair response (activation of DNA repair pathways and antioxidant mechanisms), essential to preserve genome integrity, ensuring proper germination and seedling development. The review provides an overview of priming technology, describing the range of physical-chemical and biological treatments currently available. Optimised priming protocols can be designed using the 'hydrotime concept' analysis which provides the theoretical bases for assessing the relationship between water potential and germination rate. Despite the efforts so far reported to further improve seed priming, novel ideas and cutting-edge investigations need to be brought into this technological sector of agri-seed industry. Multidisciplinary translational research combining digital, bioinformatic and molecular tools will significantly contribute to expand the range of priming applications to other relevant commercial sectors, e.g. the native seed market.

In vitro degradation of leucine in muscle, adipose tissue, liver, and kidney of fed and starved sheep.

In vitro rates of conversion of [1-14C]leucine to 4-methyl-2-oxo[1-14C]pentanoate and of oxidation of [1-14C] and [U-14C]leucine were measured for tissues from fed and starved (5 days) sheep. Slices of liver and kidney and preparations of adipose tissue and of fibre bundles of external intercostal muscle (EIC) were used. Skeletal muscle is likely the major site of leucine catabolism in sheep although adipose tissue is capable of substantial metabolism. Muscle and adipose tissue from fed sheep released 17 and 5% of the [1-14C]leucine transaminated as 4-methyl-2-oxo-[1-14C]pentanoate and upon starvation the proportions were increased (P less than 0.001) to 46 and 32%. Starvation reduced (P less than 0.01) leucine catabolism in all tissues except the kidney. The pattern of leucine catabolism in EIC muscle changed from extensive oxidation in the fed state to being limited essentially to transamination and decarboxylation in the starved state.

A yeast related ethanol intoxication syndrome in experimental calves: prevention with nystatin.

In a calf nutrition-metabolism study in which a high glucose (60% glucose and 3% lard) versus a high fat (23% glucose and 30% lard) milk replacer were compared, a syndrome characterized by anorexia, an unstable gait, depression, a distended abdomen and an odor of alcohol on the breath was observed in some calves. These signs were associated with intoxicating levels of plasma ethanol and the predominance of the yeast species Torulopsis glabrata in gastrointestinal contents of afflicted calves. Nystatin, a yeast inhibitor, was extremely useful in preventing the problem.

Glucose, acetate, and lactate metabolism in perirenal adipose tissue of fetal and newborn calves.

Rates of utilization of glucose, acetate, and lactate and activities of selected enzymes were determined in vitro to characterize the nature of lipogenesis and metabolite utilization in perirenal adipose tissue from 6- to 7-month old fetal and 3- to 4-h-old unsuckled newborn calves. Contribution of the pentose phosphate cycle to glucose metabolism was estimated using specifically labeled glucose. Rates of fatty acid synthesis from all three substrates and oxidation of glucose were much greater in fetal than in newborn adipose tissue. In fetal adipose tissue, acetate and lactate were major sources of carbon for fatty acid synthesis; glucose functioned mainly by metabolism via the pentose phosphate cycle to provide reducing equivalents for fatty acid synthesis and by incorporation into glyceride glycerol for fatty acid esterification. Pentose phosphate cycle contributed 58 and 12% to glucose metabolism in adipose tissue of fetal and newborn calves, respectively. Adipose tissue metabolism of newborn calves was characterized by greatly depressed rates of fatty acid synthesis despite high enzyme activities and elevated rates of glyceride glycerol synthesis.

Effects of age, milk replacer composition, and rumen function on lipogenesis in adipose tissue of young calves.

Rates of utilization of glucose, acetate, and lactate and activities of selected enzymes were determined in vitro to evaluate the effects of age and diet on lipogenesis in perirenal adipose tissue of calves. Three-day-old Holstein bull calves were fed up to 12 wk of age on one of three dietary treatments: a high carbohydrate milk replacer; a high fat milk replacer; and weaning at 6 wk of age from high fat replacer to calf starter. Adipose tissue biopsies were obtained from calves at 2, 5, 8, and 12 wk of age. Rates of fatty acid synthesis and activities of enzymes of the pentose phosphate and citrate cleavage pathways were increased in calves fed high carbohydrate milk replacer. These parameters were decreased in calves fed high fat replacer and were further depressed after weaning. Substrate preference for fatty acid synthesis in all calves was acetate, then lactate, then glucose. With increase in age from 2 to 12 wk, adipose tissue of calves fed milk replacer partitioned more acetate and lactate toward fatty acid synthesis and less toward oxidation. The pentose phosphate cycle was characterized by high rate of recycling and contributed at least 50% of reducing equivalents required for fatty acid synthesis. It appeared that several features of lipogenesis characteristic of functional ruminants are also shared by preruminant calves.

Growth, health, and blood glucose concentrations of calves fed high-glucose or high-fat milk replacers.

The influence of age, carbohydrate-fat ratios of milk replacers, and development of ruminal function on growth, health, and blood glucose concentrations were evaluated in calves. Colostrum-fed, 3-day-old Holstein bull calves were fed to 12 wk on one of three dietary treatments: 1) a high carbohydrate, low fat (60.5% glucose, 9.5% lactose, and 3% lard) milk replacer; 2) a low carbohydrate, high fat (23% glucose, 12.5% lactose, and 30% lard) milk replacer; and 3) weaning at 6 wk of age from high-fat replacer to a standard calf starter. The high fat milk replacer was superior to low fat milk replacer for total weight gains and efficiency of feed conversion. Rates of weight gain of starter calves were similar to those of calves fed low fat. Calves fed the diet with low fat had a high incidence of diarrhea, an occasional outbreak of a yeast-related ethanol intoxication syndrome, and high concentrations of glucose in urine. Irrespective of milk replacer composition or development of ruminal function, plasma and whole blood glucose concentrations declined rapidly in the first 6 wk. Corpuscular glucose declined steadily with age in all calves. This age-related decrease of blood glucose concentration of calves seems to be a constitutive phenomenon.

An annexin 1 (ANXA1)-derived peptide inhibits prototype antigen-driven human T cell Th1 and Th2 responses in vitro.

BACKGROUND: Annexin-1 (ANXA1, lipocortin 1) is a pleiotrophic protein produced by many cell types including peripheral blood leucocytes. Although it has been shown to inhibit "macroscopic" inflammatory processes in animal models, its direct effects on antigen-activated human T cells have not been studied. OBJECTIVE: To test the hypothesis that ANXA1-derived peptides inhibit antigen-driven prototype Th1 and Th2-type human T cell responses of clinical relevance and lectin-driven responses in vitro. METHODS: Peripheral blood mononuclear cells (PBMC) were isolated from 14 atopic subjects sensitized to house dust mite allergen (Dermatophagoides pteronyssinus, Der p) and purified protein derivative (PPD) of Mycobacterium tuberculosis. PBMC (1 x 106/mL) were cultured with phytohaemagglutinin (PHA; 5 microg/mL; 4 days), Der p (25 microg/mL; 6 days), PPD (10 microg/mL, 6 days) or medium control. Two ANXA1-derived peptides, Ac2-26 and AF-2 (5-500 microM), were assessed for possible inhibition of PHA-and antigen-induced T cell proliferation (measured by 3H-thymidine uptake), while Ac2-26 was assessed for inhibition of Der p-induced interleukin (IL)-5 release and PPD-induced interferon-gamma (IFN-gamma) release (measured by ELISA). Comparison was made with dexamethasone as an established inhibitory control. Endogenous production by PBMC of cell surface-associated and intracellular ANXA1 in response to PHA, Der p and PPD in the presence and absence of dexamethasone was measured by specific ELISA. RESULTS: Both PHA- and antigen-induced T cellular proliferation were inhibited by dexamethasone. Although neither ANXA1-derived peptide significantly altered PHA-induced proliferation, both effected concentration-dependent reductions in antigen-induced proliferation, Ac2-26 being the more potent. Peptides of identical amino acid composition to Ac2-26 and AF-2, but of random sequence, were ineffective at equivalent concentrations. In addition, Ac2-26 and dexamethasone inhibited Der p-induced IL-5 release and PPD-induced IFN-gamma release in a concentration-dependent fashion. Endogenous ANXA1 was detectable in PBMC, but at concentrations approximately 104-fold lower, in molar terms, than the effective concentrations of the exogenously added, ANXA1-derived inhibitory peptides. Endogenous production was not significantly altered by any of the T cell stimuli employed in this study, in the presence or absence of dexamethasone. CONCLUSION: In prototype Th1 and Th2-type human T cell responses, ANXA1-derived peptides can inhibit antigen-driven cellular proliferation and cytokine production.