Effect of zinc deficiency and zinc supplementation on adrenals, plasma steroids and thymus in rats

Effects of Elevating Zinc Supplementation on the Health and Production Parameters of High-Producing Dairy Cows

This study's objective was to determine the effects of increasing the dietary added zinc (Zn) on the milk production, milk somatic cell count (SCC), and immunoglobulin and antioxidant marker concentrations in the blood of dairy cows. Twelve Holstein cows (67 ± 2.5 days in milk) were assigned randomly to (1) a diet containing Zn-methionine at 76 mg/kg of DM (CTL) or (2) CTL top-dressed with about 21 mg/kg of DM extra Zn-methionine (+Zn) for 70 d. The concentrations of reduced (GSH) and oxidized (GSSG) glutathione, malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), and immunoglobulins in the blood were measured on d 0, 35, and 70. Compared to CTL, +Zn decreased the dry matter intake (DMI) throughout the trial and the milk yield (MY) during the first phase of feeding (0-35 d). It, however, increased the milk yield during the last phase (36-70 d). The +Zn tended to have lower and greater milk protein yields than CTL during the first and last feeding phases, respectively. The +Zn tended to decrease the SCC and was associated with lower plasma GSH: GSSG and lower serum SOD concentrations relative to CTL. The +Zn did not affect the immunoglobulins, MDA, or CAT. Despite the early DMI and MY reduction, the prolonged Zn-methionine supplementation at about 100 mg/kg of DM improved the milk yield, possibly as a result of the improved udder health of dairy cows.

Response of lactating dairy cows fed different supplemental zinc sources with and without evaporative cooling to intramammary lipopolysaccharide infusion: intake, milk yield and composition, and hematologic profile1

The objective of this study was to determine the effect of dietary supplemental Zn source and evaporative cooling on intake, milk yield and composition, and the rate of leukocyte migration into the mammary gland following intramammary lipopolysaccharide (LPS) infusion. Multiparous Holstein cows (n = 72) were assigned to one of four treatments with a 2×2 factorial arrangement including two sources of supplemental Zn: 75 mg/kg Zn hydroxychloride or 35 mg/kg Zn hydroxychloride + 40 mg/kg Zn-Met complex (ZMC) each with or without evaporative cooling. The cooling system was implemented by the use of fans and misters over the freestall and feeding areas. On day 34 of the experiment, cows (n = 16; days in milk = 263 ± 63 d) received an infusion of 10 μg of LPS, or a saline control, in the left or right rear quarters. Individual milk samples from both quarters were collected at -12, -4, 0, 6, 12, 24, 48, 72, 96, 120, 144, and 168 h relative to infusion and analyzed for composition and bovine serum albumin. Rectal temperature and respiration rate were assessed and blood samples were collected at the same time points (with an additional sample at 3 h) for analyses of lactose and cortisol. Complete blood counts were performed on samples collected within the first 24 h post infusion. Intramammary LPS infusion reduced (P < 0.01) milk yield, DMI and feed efficiency regardless of dietary or cooling treatments. Non-cooled cows tended (P = 0.09) to have greater feed efficiency (=milk yield/DMI) at 1 d after infusion than those subjected to cooling. Intramammary LPS infusion dramatically increased (P < 0.01) milk somatic cell count (SCC) but treatments had no apparent impact on milk SCC. Compared with cooled cows, non-cooled cows had greater (P < 0.05) plasma lactose concentrations, but lower (P < 0.03) blood concentrations of neutrophils and lymphocytes at 3 h post infusion. This suggests a greater leukocyte migration into the mammary gland of heat-stressed cows. In conclusion, noncooled cows tended to maintain greater feed efficiency and appeared to have greater leukocyte migration into the mammary gland immediately after intramammary LPS infusion compared with cooled cows. Dietary supplemental Zn source had no impact on measures assessed after intramammary LPS infusion.

Roles of Zinc Signaling in the Immune System

Zinc (Zn) is an essential micronutrient for basic cell activities such as cell growth, differentiation, and survival. Zn deficiency depresses both innate and adaptive immune responses. However, the precise physiological mechanisms of the Zn-mediated regulation of the immune system have been largely unclear. Zn homeostasis is tightly controlled by the coordinated activity of Zn transporters and metallothioneins, which regulate the transport, distribution, and storage of Zn. There is growing evidence that Zn behaves like a signaling molecule, facilitating the transduction of a variety of signaling cascades in response to extracellular stimuli. In this review, we highlight the emerging functional roles of Zn and Zn transporters in immunity, focusing on how crosstalk between Zn and immune-related signaling guides the normal development and function of immune cells.

Nutritionally mediated programming of the developing immune system

A growing body of evidence highlights the importance of a mother's nutrition from preconception through lactation in programming the emerging organ systems and homeostatic pathways of her offspring. The developing immune system may be particularly vulnerable. Indeed, examples of nutrition-mediated immune programming can be found in the literature on intra-uterine growth retardation, maternal micronutrient deficiencies, and infant feeding. Current models of immune ontogeny depict a "layered" expansion of increasingly complex defenses, which may be permanently altered by maternal malnutrition. One programming mechanism involves activation of the maternal hypothalamic-pituitary-adrenal axis in response to nutritional stress. Fetal or neonatal exposure to elevated stress hormones is linked in animal studies to permanent changes in neuroendocrine-immune interactions, with diverse manifestations such as an attenuated inflammatory response or reduced resistance to tumor colonization. Maternal malnutrition may also have a direct influence, as evidenced by nutrient-driven epigenetic changes to developing T regulatory cells and subsequent risk of allergy or asthma. A 3rd programming pathway involves placental or breast milk transfer of maternal immune factors with immunomodulatory functions (e.g. cytokines). Maternal malnutrition can directly affect transfer mechanisms or influence the quality or quantity of transferred factors. The public health implications of nutrition-mediated immune programming are of particular importance in the developing world, where prevalent maternal undernutrition is coupled with persistent infectious challenges. However, early alterations to the immune system, resulting from either nutritional deficiencies or excesses, have broad relevance for immune-mediated diseases, such as asthma, and chronic inflammatory conditions like cardiovascular disease.

Anxiety-like behavior of young rats after 2-week zinc deprivation

The relationship between neuronal function in the brain and neuropsychological behavior were analyzed in young rats fed a zinc-deficient diet for 1-2 weeks. Serum zinc concentration was less than 50% of that of the control. However, zinc concentration in the hippocampal perfusate measured by the in vivo microdialysis was not decreased after 2-week zinc deprivation. Timm's stain, with which histochemically reactive zinc in the presynaptic vesicle is detected, was not also attenuated in the brain. On the other hand, serum corticosterone concentration, which was determined in the morning, was markedly increased after 2-week zinc deprivation and intracellular calcium signal, which was determined by fura-2 AM, was also increased in the hippocampus. In the hippocampus in zinc deficiency, intracellular free calcium concentration may be altered prior to the decrease in zinc concentration in the extracellular fluid. When rats were subjected to the open-field test, the frequency of line crossing and the time of grooming were decreased after 2-week zinc deprivation. In the plus-maze test, the time spent in the open arms was also decreased in zinc-deficient rats, suggesting that anxiety-like behavior is increased in zinc deficiency. The present study indicates that the increase in anxiety-like behavior in zinc deficiency may be linked to the increased concentration of basal free calcium in hippocampal cells, probably due to the increase in serum corticosterone concentration.

Energetic and nutritional regulation of the adaptive immune response and trade-offs in ecological immunology

Ecological Immunology views immunocompetence as a costly process involving trade-off decisions among competing nutrient demands by different life-history traits. This review examines immunocompetence fitness costs in light of recent work on the role the energetic and nutritional status of the host plays in the regulation of the adaptive T-helper lymphocyte response. Three phenotypically distinct T-lymphocyte populations have been identified: the Th1 response, important in protecting against intracellular infections; the Th2 response, important in protecting against noninvasive infections such as helminthes; and the Th3 or Treg population, which downregulates polarized Th1 or Th2 responses. A strong Th1 response is protective against intracellular infections, while a Th2 response is protective against noninvasive infections. Adequate zinc and energy intake leads to a dominant Th1 response and a downregulated Th2 response, while deficiencies of either of these results in activation of the Th2 response and downregulation of the Th1 response. In contrast, adequate vitamin A intake leads to an activated Th2 response and downregulation of the Th1 response, while vitamin A deficiency reverses these patterns. These differential immune regulatory effects of energy and nutrient intake will have distinct effects on specific stages of the natural history of different pathogen infections where the protective roles of the Th1-Th2 responses are distinct. Accordingly, fitness costs of immunocompetence are more complex than currently proposed since trade-offs in energetic and nutritional resources produce cross-regulatory effects on immune system subcomponents.

Water maze performance and changes in serum corticosterone levels in zinc-deprived and pair-fed rats

The aims of the present study were (1) to evaluate the learning and short- and long-term memory of zinc-deprived (ZD) and pair-fed (PF) rats in a Morris water maze (MWM) and (2) to monitor the serum corticosterone levels of these rats before and after swimming. Young Sprague-Dawley rats (aged 27-31 days) consumed AIN-93G diet for 10 days, and then were separated into ad libitum control (CT), PF and ZD groups. The zinc content of the diet was 25-30 ppm (CT and PF) or <1 ppm (ZD). After 17 days on experimental diets, a MWM was used to test spatial cognition. Delayed-matching-to-place (DMP) test results indicate that both zinc deprivation and food restriction had no effect on short-term memory. The PF rats exhibited significantly impaired learning and thigmotaxia (i.e., wall hugging) in the learning test. The PF group also demonstrated less preference for the target zone in the first 15 s of the probing test. When the total 120 s of the probing test was considered, there were no differences in preference for the target zone, but thigmotaxia was greater in the PF than the CT group. The only behavioral change of the ZD group was thigmotaxia observed during the 120-s probing test following training, indicating the increment of anxiety. Morning basal corticosterone levels before swim training were significantly elevated in the PF group on Day 15 of dietary treatment, whereas a significant elevation of the basal corticosterone level in the ZD group was not statistically significant until Day 22. The data indicate an association between impaired learning, poor searching strategy and elevated corticosterone in the PF group. In contrast, the ZD rats showed normal cognitive performance but had elevated corticosterone and increased anxiety-like behavior (thigmotaxia).

Effects of zinc deficiency and corticosterone elevation on bone marrow in rats

OBJECTIVE

The effects of zinc deficiency and serum corticosterone elevation, in a zinc-deficient state, on rat bone marrow were studied.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into the following four groups: zinc-adequate (ZA), restricted ZA (RZA), zinc-deficient (ZD) and ZD with the injection of Mifepristone (ZD+Mife). Platelet and reticulocyte counts, levels of serum zinc and corticosterone, bone marrow cellularity and morphological alterations of marrow were examined in all rats.

RESULTS

Decreased marrow cellularity, decreased numbers of peripheral platelets and reticulocytes, and increased adipocytes in the marrow were observed in ZD rats. The injection of Mifepristone improved marrow cellularity, and increased the number of platelets, while decreasing adipocytes in the marrow in ZD rats.

CONCLUSION

Both zinc deficiency itself and the associated serum corticosterone elevation induced bone marrow suppression in rats.

Melanin: the organizing molecule

The hypothesis is advanced that (neuro)melanin (in conjunction with other pigment molecules such as the isopentenoids) functions as the major organizational molecule in living systems. Melanin is depicted as an organizational "trigger" capable of using established properties such as photon-(electron)-phonon conversions, free radical-redox mechanisms, ion exchange mechanisms, and semiconductive switching capabilities to direct energy to strategic molecular systems and sensitive hierarchies of protein enzyme cascades. Melanin is held capable of regulating a wide range of molecular interactions and metabolic processes primarily through its effective control of diverse covalent modifications. To support the hypothesis, established and proposed properties of melanin are reviewed (including the possibility that (neuro)melanin is capable of self-synthesis). Two "melanocentric systems"--key molecular systems in which melanin plays a central if not controlling role--are examined: 1) the melanin-purine-pteridine (covalent modification) system and 2) the APUD (or diffuse neuroendocrine) system. Melanin's role in embryological organization and tissue repair/regeneration via sustained or direct current is considered in addition to its possible control of the major homeostatic regulatory systems--autonomic, neuroendocrine, and immunological.

The production of zinc deficiency in the guinea pig

A diet which contained less than 1 microgram Zn per g was eaten readily by guinea pigs. No signs of zinc deficiency were produced unless the animals were deprived of access to zinc-supplemented solid food from birth and were maintained on grid floors to prevent coprophagy or ingestion of sawdust bedding material. At an early stage of deficiency, plasma zinc concentration, food intake and growth were reduced and large regular variations of food intake (food cycling) were observed. More severe deficiency produced decreases in the zinc content of other tissues and characteristic epidermal lesions. The requirement of guinea pigs for zinc for growth is probably about 2.5 micrograms per g feed which is much lower than for calves, rats and pigs.

Passive avoidance performance of mice fed marginally or severely zinc deficient diets during post-embryonic brain development

Swiss-Webster outbred mice were fed marginally or severely zinc deficient diets (9 or 2 ppm zinc) from day 16 gestation to day 15 postnatal. Control mice were fed a 100 ppm diet either ad lib or in amounts equal to the diet intake of deprived mice (pair fed controls). Male and female offspring were tested at 70 days of age in a one-trial passive avoidance task with a 30 min train-test interval. Both marginally and severely zinc deprived offspring (but not pair fed controls) had shorter avoidance latencies than offspring of ad lib fed zinc replete controls. Zinc deprived offspring did not differ from control mice when either baseline or "stressed" (exposure to novel environment) plasma corticosterone levels were quantitated. Further, zinc staining patterns of the hippocampus (Timm-sulfide stain) were not altered in the nutritionally deprived offspring. Thus marginal dietary zinc deficiency during development can lead to impaired passive avoidance performance in adult mice. This behavioral effect is not associated with altered pituitary-adrenocortical activity or with a permanent reduction in hippocampal zinc staining. This result has significant implications for the influence of zinc deprivation in utero and in the neonatal animal on adult behavior characteristics.

Interaction of nutrition and infection: effect of zinc deficiency on resistance to Trypanosoma musculi

1. Zinc deficiency was studied in mice infected with Trypanosoma musculi. 2. In all dietary groups, the infected animals consumed more food and gained more weight than the uninfected controls. 3. In all studies, at the peak of parasitemia, the zinc-deficient animals showed three times the number of trypanosomes as that of the complete and pair-fed mice. 4. The average coefficients of variation in body lengths of T.musculi cells indicated that the formation of the reproductive-inhibiting antibody (ablastin) occurred later in zinc-deficient animals compared to animals fed complete diets. The degree and duration of parasitemia in the zinc-deficient animals indicated a delay in the synthesis of the terminal lytic antibody. 5. Irrespective of diets, severe depression in the primary and secondary antibody responses to in vivo immunization of sheep erythrocytes was observed in infected animals over non-infected controls.