Effect of vitamin A deficiency and Newcastle disease virus infection on IgA and IgM secretion in chickens.

The effect of vitamin A deficiency or the lentogenic La Sota strain of Newcastle disease virus (NDV) infection, or both, on immunoglobulin (IgA and IgM) levels in bile and plasma were investigated. In addition, tissue distribution of IgA-, IgG- and IgM-containing cells was studied to establish the source of these Ig. Chickens (1-d-old) with limited vitamin A reserves were fed ad lib. on diets containing either marginal or adequate levels of vitamin A. At 4 weeks of age, half the chickens in each group were infected with NDV. The number of IgA- and IgM-containing cells was not significantly affected by vitamin A deficiency, demonstrating that neither class-switching nor homing of Ig-containing cells is influenced by vitamin A deficiency. Although bile IgM levels were not significantly different in vitamin A-deficient chickens compared with normal chickens, IgA levels were significantly lower. This decrease was even more pronounced in deficient NDV-infected chickens, despite the higher number of IgA-containing cells found in these birds. These results, together with the slightly increased levels of IgA in plasma of vitamin A-deficient chickens, suggest that the hepatobiliary transport of IgA is impaired by vitamin A deficiency and possibly also by NDV infection, although disturbed secretion by IgA-containing cells cannot be excluded.

Production of chickens with marginal vitamin A deficiency.

Marginally vitamin A-deficient 1-d-old chickens capable of remaining healthy for at least 6 weeks were produced using a two-generation model. In this model, hens fed on diets with a limited vitamin A content were used to obtain 1-d-old chickens which were marginally deficient in vitamin A. Only hens with a narrow range of plasma retinol values (0.60-0.85 mumol/l) were satisfactory for this purpose. Above this range the 1-d-old chickens were not marginally vitamin A deficient. Below this range egg production and hatchability were affected to some extent depending on the degree of vitamin A deficiency. Even when egg production and hatchability remained at a high level in such birds, the 1-d-old chickens produced were not sufficiently strong to survive the first weeks of life. The advantages of the two-generation model for producing marginally vitamin A-deficient chickens are the increased uniformity and predictability of the chickens with respect to body-weight, general health and vitamin A status. However, it does take about 3 months to produce such chickens.

Effects of vitamin A deficiency and Newcastle disease virus infection on lymphocyte subpopulations in chicken blood.

The effect of vitamin A deficiency and Newcastle disease virus (NDV)-infection on peripheral blood lymphocytes (PBL) was studied by differential cell counting and flow cytometry. Day-old chickens were fed purified diets containing either marginal or adequate levels of vitamin A and at 26 days of age half of the chickens in each group were infected with NDV. The absolute numbers of PBL and their subpopulations were studied until 10 days after infection. Vitamin A deficiency resulted in significantly lower numbers of PBL throughout the experiment. NDV-infection produced lymphopenia during the first 3 days, followed by a strong increase in PBL numbers after 6 days. Both changes in PBL were less pronounced in vitamin A-deficient birds. For flow cytometric analysis monoclonal antibodies reacting specifically with B-cells or a subpopulation of T-cells were used. Vitamin A-induced lymphopenia could be attributed to a decreased number of PBL, negative for both antibodies, and to the absence of an increase in B-cells which normally occurs at this age. The negative cells are suggested to represent, at least partially, cytotoxic T-cells, which may explain the impaired cytotoxic T-cell-activity found in earlier studies. NDV-induced lymphopenia and subsequent increase of PBL could be attributed to all cell types investigated. However, in vitamin A-deficient birds negative cells did not show these reactions. Therefore, it can be concluded that vitamin A deficiency has a detrimental effect on PBL, negative for both antibodies used, and on the normal growth of the number of B-cells at this age.

Epithelia-damaging virus infections affect vitamin A status in chickens.

The effect of infection with infectious bronchitis virus (IBV) and reovirus (RV) on vitamin A status was investigated in chickens with a normal or marginal intake of vitamin A. At the age of 4 wk, chickens were infected with either IBV or RV, primarily affecting the respiratory or intestinal tract, respectively. Both viruses lowered plasma retinol levels significantly. The effect was more pronounced in chickens fed a diet marginally deficient in vitamin A than in those fed a diet adequate in vitamin A. Concentrations of retinol-binding protein, transthyretin and albumin in RV-infected chickens were also significantly lower than in noninfected chickens fed the same diets; in chickens infected with IBV, there was no effect. These results suggest that the reduced vitamin A status of IBV-infected chickens could be attributed to increased rate of utilization by tissues. In RV infection, this mechanism could be involved but impaired absorption of nutrients (including vitamin A) and direct loss of nutrients via the intestinal tract could also be important.

Effect of vitamin A deficiency on the activity of macrophages in Newcastle disease virus-infected chickens.

The effect of vitamin A deficiency on the activity of peritoneal macrophages (PM) was investigated in noninfected and Newcastle disease virus (NDV)-infected chickens. Day-old chickens with limited vitamin A reserves were fed diets containing either marginal (120 retinol equivalents (RE)/kg) or adequate (1200 RE/kg) levels of vitamin A. At 4 weeks of age, half of the chickens in each group were infected with the La Sota strain of NDV and PM were isolated 11 or 12 days later. These were used for counting the uptake of fluorescein isothiocyanate-labeled yeast cells as an indicator of phagocytic activity and for measuring the reduction of nitroblue tetrazolium (NBT), which provides an estimate of oxygen-dependent killing of microorganisms. Vitamin A deficiency impaired NBT reduction and, to a lesser extent, phagocytosis in both infected and noninfected chickens. NDV infection increased phagocytosis and NBT reduction in normal and, to a lesser extent, in vitamin A-deficient chickens.

Changes in lymphoid organs and blood lymphocytes induced by vitamin A deficiency and Newcastle disease virus infection in chickens.

The effect of vitamin A deficiency in the presence or absence of Newcastle disease virus infection (NDV, La Sota strain) on weight of lymphoid organs and on the number and type of circulating white blood cells (WBC) was investigated in chickens. Day-old chickens with limited vitamin A reserves were fed purified diets containing either marginal (ad libitum) or adequate (pair-fed) levels of vitamin A and at 21-28 days of age; half the chickens in each group were infected with NDV. Vitamin A deficiency resulted only in significantly lower absolute and relative weights of bursa of Fabricius and after infection both weights of bursa and thymus were significantly lower. Relative weight of spleen was significantly higher after infection irrespective of vitamin A status. Liver weights were not affected by vitamin A status and/or NDV infection. Both vitamin A deficiency and NDV infection resulted in lymphopenia, while the lowest number of WBC were observed in vitamin A-deficient chickens during the acute phase of NDV (5 days after infection). Subsequent to lymphopenia due to NDV infection, a marked lymphocytosis was observed in controls and to a lesser extent in vitamin A-deficient birds. These results indicate that vitamin A deficiency, which is aggravated by concomitant NDV infection, affects lymphoid cell systems.

Vitamin A deficiency impairs cytotoxic T lymphocyte activity in Newcastle disease virus-infected chickens.

The effect of vitamin A deficiency on cytotoxic T lymphocyte (CTL) activity was investigated during the acute phase of disease 7 days after primary inoculation and 1 day after secondary inoculation in chickens with or without Newcastle disease virus (NDV, La Sota strain) infection. Day-old chickens with limited vitamin A reserves were fed purified diets containing either marginal (ad libitum) or adequate (pair-fed) levels of vitamin A, and at 3 weeks of age half of the chickens in each group were infected with NDV. Cytotoxic activity was investigated during the acute phase of disease (7 days after primary inoculation) and 1 day after secondary inoculation, in an assay system with either peripheral blood lymphocytes (PBL) or nonadherent splenocytes as effector cells and adherent splenocytes from the same animal as target cells. After primary inoculation, cytotoxic activity could only be demonstrated in nonadherent splenocytes. Vitamin A deficiency resulted in significantly reduced CTL activity at all effector/target cell ratios tested. After reinfection CTL activity could also be demonstrated in PBL, but only from chickens fed the control diet, suggesting a diminished pool of CTL in vitamin A deficiency. The results of this study indicate that vitamin A deficiency impairs CTL activity - a part of the cell-mediated defense system - and this may have important implications for recovery from viral infection.

Objective clinical examination of poultry as illustrated by the comparison of chickens with different vitamin A status.

One day old pullets derived from marginally vitamin A deficient laying hens were fed diets containing either adequate or marginal amounts of vitamin A. At the age of 34 days, animals fed the diet low in vitamin A had group mean plasma concentrations of retinol which were one tenth the mean plasma concentrations of controls. When compared with their controls, the deficient animals displayed body weights which were on average 16% less. Of 20 pullets per dietary group one control animal and 9 deficient animals died by the age of 34 days. At the age of 29 days, control (n = 16) and deficient chickens (n = 11) were examined clinically by assigning scores to a number of parameters. Three assessors carried out the examination independently. The birds were presented for examination at random and their treatment groups were not disclosed to the assessors. Out of 26 parameters assessed quantitatively per individual animal, only three parameters discriminated between control and deficient chickens. Deficient animals grew poorly, had a hunched up posture and increased fluid content in faeces. Classical signs of chronic vitamin A deficiency in domestic fowl such as bone deformities, keratinization of the tongue and decreased transparency of the cornea were not observed.

The interaction between vitamin A status and Newcastle disease virus infection in chickens.

Newcastle disease virus (NDV) infection in chickens differing in vitamin A status has been selected as a model to examine the interrelationship between marginal vitamin A deficiency and the severity of consequences of measles infection in humans. Day-old chickens with limited vitamin A reserves, the progeny of marginally vitamin A-deficient hens, were fed purified diets containing either marginal (120 retinol equivalents/kg diet, ad libitum) or adequate (1200 retinol equivalents/kg diet, ad libitum or pair-fed) levels of vitamin A for a period of 10 wk. At 4 wk of age, half of the chickens in each group were infected intraocularly with the lentogenic, i.e., mildly pathogenic, La Sota strain of NDV. Within 1 wk of infection, plasma retinol levels in the infected, marginally vitamin A-deficient chickens showed a significant and persistent decrease compared to their noninfected counterparts fed the same diet. Moreover, infection with NDV resulted in increased rates of morbidity in the marginally vitamin A-deficient chickens compared with nondeficient chickens. The results of this study indicate that pre-existing marginal vitamin A status increases the severity of disease following NDV infection, and that infection with NDV reduces marginal plasma vitamin A levels to levels which can be regarded as deficient.

Effect of Newcastle disease virus infection on vitamin A metabolism in chickens.

The effect of Newcastle disease virus (NDV, La Sota strain) infection on vitamin A metabolism was investigated in chickens maintained on normal or marginal vitamin A intake. NDV, a virus of the Paramyxoviridae family that primarily affects epithelial tissue, was administered at 4 wk of age. Plasma levels of retinol, retinol-binding protein and, to a lesser extent, transthyretin were found to be significantly lower during both the acute and postacute phases of infection in chickens fed a diet marginally deficient in vitamin A compared to noninfected birds fed the same diet, while vitamin A content in liver was unaffected. However, in chickens fed adequate vitamin A, NDV infection did not influence the parameters measured. Levels of retinol-binding protein in liver were significantly increased by inadequate vitamin A nutriture, but infection partly reduced this increase. The results suggest that the reduced vitamin A status in marginally vitamin A-deficient chickens infected with NDV can be attributed to a combination of a direct effect of the virus on retinol-binding protein metabolism in liver and an increased rate of utilization and catabolism of retinol and retinol-binding protein by extrahepatic tissues.

Effects of human diets on biotransformation enzyme activity and metabolic activation of carcinogens in rat liver.

We studied the effects of a complete human diet, based on mean consumption figures in The Netherlands, the heating of food, and the presence of vegetables and fruit in the diet on the drug metabolizing capacity of the rat liver and on metabolic activation of known carcinogens. Groups of five male and five female Wistar rats were given ad lib. one of six different diets for 3 months. Each diet contained 40 energy (E)% fat, 13 E% protein, 47 E% carbohydrate and 5% fibre (w/w). The diets were as follows: a control diet of semi-synthetic materials (A); a human diet of meat, bread and eggs without processing (B); diet B heated under usual household conditions (C); a diet representing a complete human meal including (summer) vegetables and fruit (D); diets consisting of winter vegetables (E) or summer vegetables (F) with fruit. Semi-synthetic components were added to diets B-F to achieve the desired composition. There were differences between male and female rats on the effects of the different diets on hepatic enzyme activity. In female rats, but not in males, ethoxyresorufin-O-deethylase activity was increased significantly (P less than 0.05) in groups C, D and E in comparison with the controls (group A). In male rats ethoxycoumarin-O-deethylase activity was enhanced in groups D, E and F, and glutathione-S-transferase was markedly induced in group F (P less than 0.01). In males, hepatic cytochrome P-450 was significantly (P less than 0.05) increased in groups B, C and E. There was no effect on aminopyrine-N-demethylase activity and almost no effect on UDP-glucuronyltransferase activity in either sex. Microsomes from rats fed heated food (C) markedly increased the mutagenicity of benzo[a]pyrene (B[a]P) in the Ames assay using Salmonella typhimurium strain TA98, in comparison with levels using microsomes from rats fed the raw food (B). Vegetables and fruit decreased B[a]P mutagenicity. All human diets except D decreased the mutagenicity of N-nitrosodimethylamine in tester strain TA100. The results indicate that the influence of components of human diets on rat-liver drug metabolism may have quite different effects on the biotransformation of carcinogens activated by different metabolic pathways.

A co-cultivation system consisting of primary chick embryo hepatocytes and V79 Chinese hamster cells as a model for metabolic cooperation studies.

In this study the role of metabolic cooperation was investigated in a co-cultivation system consisting of primary chick embryo hepatocytes and V79 Chinese hamster cells. A morphological study showed that, in addition to the gap junctions formed between homologous cells, gap junctions were formed also between the primary chick embryo hepatocytes and the V79 Chinese hamster cells. The number of gap junctions present in this system decreased in the following order: hep.-hep., V79-V79, hep.-V79. Under control conditions this number was constant during a co-cultivation period of 48 h. The heterologous gap junctions allowed the passage of 3H-labelled hypoxanthine. Addition of 12-O-tetradecanoylphorbol-13-acetate inhibited this transfer in a dose-related way. Electron microscopical studies with sectioned material showed that inhibition of transfer was paralleled by the disappearance of all gap junctions. There was a remarkable difference between the response time of the different types of gap junctions. Those formed between V79 cells had disappeared after 20 min, whereas those formed between hepatocytes had disappeared after 12 h. The heterologous gap junctions behaved more or less like those between hepatocytes. After exposure times longer than 7 h the transfer of [3H] hypoxanthine was partly restored and morphologically the gap junctions reappeared. When the V79 cells were pretreated with mitomycin C no recovery of intercellular communication was observed, indicating that the adaptation phenomenon is related to the mitotic index of the cells. Dimethylbenzanthracene inhibited the transfer of labelled nucleotides and may be the first example of an indirectly acting inhibitor of intercellular communication.