Lipid peroxidation in mitochondria and microsomes from adult and fetal rat tissues

Pregnant female Wistar rats that received a control (100 ppm Zn) or a Zn-deficient diet (1.5 ppm Zn) from d 0 to 21, or nonpregnant normally fed female rats without or with five daily oral doses of 300 mg/kg salicylic acid were used for the experiments. In isolated mitochondria or microsomes from various maternal and fetal tissues, lipid peroxidation was determined as malondialdehyde formation measured by means of the thiobarbiturate method. Zn deficiency increased lipid peroxidation in mitochondria and microsomes from maternal and fetal liver, maternal kidney, maternal lung microsomes, and fetal lung mitochondria. Lipid peroxidation in fetal microsomes was very low. Zn deficiency produced a further reduction of lipid peroxidation in fetal liver microsomes. Salicylate increased lipid peroxidation in liver mitochondria and microsomes after addition in vitro and after application in vivo. The increase of lipid peroxidation by salicylate may be caused by two mechanisms: an increased cellular Fe uptake that, in turn, can increase lipid peroxidation and chelating Fe, in analogy to the effect of ADP in lipid peroxidation. The latter effect of salicylate is particularly expressed at increased Fe content.     

Changes in hypothalamic noradrenergic systems during the anorexia of zinc deficiency

Pregnant Wistar rats fed control and Zn-deficient diets received daily oral doses of 0, 100, and 300 mg/kg sodium valproate from d 16 to 20 of gestation. Only the highest valproate doses induced a small reduction in fetal body weight in the normally fed group. Zinc deficiency caused a drastic reduction in maternal and only a small reduction in fetal serum Zn concentrations. Valproate treatment had no effect on maternal and fetal serum Zn concentrations. Valproate reduced fetal liver Zn content only in the normally fed group. The reduction of liver Zn content resulted from the reduction of Zn-metallothionein. Valproate did not affect total Zn and Zn-metallothionein in kidneys. Three percent of the Zn-deficient fetuses developed hydronephrosis and hydrops. Valproate treatment drastically enhanced the occurrence of fetal hydronephrosis and hydrops. Valproate induced fetal liver necroses, independent of Zn nutrition.     

Effects of salicylate and zinc deficiency on the serum concentrations of magnesium,calcium, and parathyroid hormone

Oral application of 700 mg/kg salicylic acid to pregnant and nonpregnant female rats caused an increase of serum Mg²⁺ and a decrease of serum Ca²⁺ concentration. The salicylate effect was drastically enhanced by Zn deficiency. The increase in serum Mg²⁺ is probably caused by the nephrotoxicity of salicylate. The decrease of serum Ca²⁺ concentration is combined with an increase of parathyroid hormone concentration in serum. Probably, salicylate and Zn deficiency inhibit Ca²⁺ mobilization by parathyroid hormone in bone.     

Alfalfa genotypes differ in their ability to tolerate zinc deficiency

Response of 13 alfalfa (Medicago sativa L.) genotypes to varied Zn supply (+Zn: 2 mg kg⁻¹ soil, −Zn: no added Zn) was studied in a pot experiment under controlled environmental conditions. Plants were grown for four weeks in a Zn-deficient siliceous sandy soil. Plants grown at no added Zn showed typical Zn deficiency symptoms i.e. interveinal chlorosis of leaves, yellowish-white necrotic lesions on leaf blades, necrosis of leaf margins, smaller leaves and a marked reduction in growth. There was solute leakage from the leaves of Zn-deficient plants, while no solute leakage from Zn-sufficient plants. The ratios of P:Zn, Fe:Zn, Cu:Zn and Mn:Zn in Zn-deficient plants were extremely high compared with Zn-sufficient plants indicating disturbance of P:Zn, Fe:Zn, Cu:Zn and Mn:Zn balance within plant system by Zn deficiency. Genotypes differed markedly in Zn efficiency based on shoot dry matter production. Alfalfa genotypes also differed markedly in P:Zn ratio, Cu:Zn ratio and Fe:Zn ratio under —Zn treatment. The shoot dry weight, shoot:root ratio, chlorophyll content of fresh leaf tissue, solute leakage from the leaves, Zn uptake and distribution of Zn in shoots and roots were the most sensitive parameters of Zn efficiency. Zn-efficient genotypes had less solute leakage but higher shoot:root ratio and higher Zn uptake compared with Zn-inefficient genotypes. Under —Zn treatment, Zn-inefficient genotypes had less Zn partitioning to shoots (33–37%) and more Zn retained in roots (63–67%), while Zn-efficient genotypes had about equal proportions of Zn in roots (50%) and shoots (50%). This revised version was published online in June 2006 with corrections to the Cover Date.     

Development of fetal mineral and trace element metabolism in rats with normal as well as magnesium- and zinc-deficient diets

At d 17 of gestation, the concentrations of K, Mg, Mn, and Zn in fetal rat serum, measured by flame photometry and atomic absorption spectrophotometry, were higher than in maternal serum and declined thereafter. The serum concentrations of protein and Cu increased, whereas the Na concentration remained constant during perinatal development. In Mg and Zn deficiency, the concentrations of Mg and Zn in fetal serum were less reduced than in maternal serum. During perinatal development, the contents of K and Mg in fetal liver decreased continuously, whereas the contents of Zn and Cu transiently increased, reaching a peak at 1 and 7 d after birth. The decrease of Mg in fetal liver was caused by a reduction of Mg in the nuclei and microsomes. The transient increase of Zn content in fetal liver resulted from the induction of Zn-metallothionein, as determined by Sephadex G-75 gel filtration. Magnesium deficiency had no significant effect on Mg content of fetal and perinatal liver. In Zn deficiency, induction of Zn-metallothionein in fetal liver was delayed and reduced. Zinc content in fetal kidneys was not significantly changed by Zn deficiency.     

Effects of zinc and/or iron deficiency on rectal temperature in rats

O'Dell et al. reported that rectal temperature was decreased by zinc deficiency in rats. However, it is not known whether a combined deficiency of zinc and iron affects rectal temperature. Forty 4-wk-old male Sprague-Dawley rats were assigned into four dietary treatment groups of 10 rats each for the 4-wk study: zinc-deficient group (4.5 mg Zn and 35 mg Fe/kg diet; −Zn), iron-deficient group (30 mg Zn/kg diet, no supplemental iron; −Fe), zinc/iron-deficient group (4.5 mg Zn/kg diet, no supplemental iron; −Zn−Fe), and control group (AIN-93G; Cont). At d 24–27, the rectal temperature was determined. The rectal temperature of the −Zn group was significantly lower than the Cont group. The rectal temperature of the −Zn−Fe group was similar to that of the Cont group, although thyroid-stimulating hormone and total thyroxin concentrations were the lowest in the −Zn−Fe group among all groups. The pattern of the plasma nitrate/nitrite concentrations across groups was similar to rectal temperature. Although observation of the rectal temperature is not conclusive, the balance between zinc and iron intake seems to determine the body temperature set point. These results suggest that the thermogenic effect of thyroid hormones is not throught to influence the paradoxical maintenance of rectal temperature in combined deficiency of zinc and iron.     

Zinc deficiency decreases plasma erythropoietin concentration in rats

In 1985, Paterson and Bettger found hypoplastic hematopoiesis in severely zinc-deficient rats. Therefore, we investigated plasma erythropoietin concentration in zinc-deficient rats. Forty 4-wk-old male Sprague-Dawley rats were assigned into 4 dietary treatment groups of 10 for the 4-wk study: zinc-deficient group (4.5 mg zinc and 35 mg iron/kg; −Zn), iron-deficient group (30 mg zinc/kg, no supplemental iron; −Fe), zinc/iron-deficient group (4.5 mg zinc/kg, no supplemental iron; −Zn−Fe), and control group (AIN-93G; Cont). Water intake determined at d 19 was similar among all treatment groups. At d 27–28, bioimpedance was measured. The intracellular water/extracellular water ratio was significantly increased in the −Zn group (p<0.05). Compared to the Cont, group, the plasma erythropoietin concentration was increased by iron deficiency and decreased by zinc deficiency (p<0.01). Hematocrit was significantly decreased in both the −Fe and −Zn−Fe groups and was significantly increased in the −Zn group (p<0.01). Transferrin saturation in the −Fe and −Zn−Fe groups was significantly lower than the Cont group (p<0.01), and that of the −Zn group was highest among all groups. The low plasma erythropoietin concentration might account for depressed hematopoiesis associated with zinc deficiency.     

Induction of hepatic metallothionein by salicylate in adult rats

Application of salicylate increased the concentration of metallothionein (MT) in liver of pregnant rats as well as of adult male rats, whereas in fetal liver, MT was reduced by salicylate. Induction of MT synthesis by salicylate is an indirect effect because in cultured hepatocytes salicylate did not induce MT synthesis. Salicylate increased MT also in adrenalectomized rats. Indomethacin induced the same concentration of MT in maternal liver as salicylate. However, indomethacin had no effect on MT in fetal liver. Induction of MT in adult liver by salicylate and indomethacin was independent of zinc.     

Root exudation and Fe uptake and transport in wheat genotypes differing in tolerance to Zn deficiency

Tolerance to Zn deficiency in wheat germplasm may be inversely related to uptake and transport of Fe to shoots. The present study examined eight bread (Triticum aestivum) and two durum (T. turgidum L. conv. durum) wheat genotypes for their capacity to take up and transport Fe when grown under either Fe or Zn deficiency. Bread wheat genotypes Aroona, Excalibur and Stilleto showed tolerance to Zn and Fe deficiency, while durum wheat genotypes are clearly less tolerant to either deficiency. Roots of bread wheats tolerant to Zn deficiency exuded more phytosiderophores than sensitive bread and durum genotypes. Greater amounts of phytosideophores were exuded by roots grown under Fe than Zn deficiency. A relatively poor relationship existed between phytosiderophore exudation or the Fe uptake rate and relative shoot growth under Fe deficiency. At advanced stages of Zn deficiency, genotypes tolerant to Zn deficiency (Aroona and Stilleto) had a greater rate of Fe uptake than other genotypes. Zinc deficiency depressed the rate of Fe transport to shoots in all genotypes in early stages, while advanced Zn deficiency had the opposite effect. Compared with Zn-sufficient plants, 17-day-old Zn-deficient plants of genotypes tolerant to Zn deficiency had a lower rate of Fe transport to shoots, while genotypes sensitive to Zn deficiency (Durati, Yallaroi) had the Fe transport rate increased by Zn deficiency. A proportion of total amount of Fe taken up that was transported to shoots increased with duration of either Fe or Zn deficiency. It is concluded that greater tolerance to Zn deficiency among wheat genotypes is associated with the increased exudation of phytosiderophores, an increased Fe uptake rate and decreased transport of Fe to shoots. This revised version was published online in June 2006 with corrections to the Cover Date.     

Expression of high zinc efficiency of Aegilops tauschii and Triticum monococcum in synthetic hexaploid wheats

The effect of varied zinc (Zn) supply on shoot and root dry matter production, severity of Zn deficiency symptoms and Zn tissue concentrations was studied in two Triticum turgidum (BBAA) genotypes and three synthetic hexaploid wheat genotypes by growing plants in a Zn-deficient calcareous soil under greenhouse conditions with (+Zn=5 mg kg^-1 soil) and without (−Zn) Zn supply. Two synthetic wheats (BBAADD) were derived from two different Aegilops tauschii (DD) accessions using same Triticum turgidum (BBAA), while one synthetic wheat (BBAAAA) was derived from Triticum turgidum (BBAA) and Triticum monococcum (AA). Visible symptoms of Zn deficiency, such as occurrence of necrotic patches on leaves and reduction in shoot elongation developed more rapidly and severely in tetraploid wheats than in synthetic hexaploid wheats. Correspondingly, decreases in shoot and root dry matter production due to Zn deficiency were higher in tetraploid wheats than in synthetic hexaploid wheats. Transfer of the DD genome from Aegilops tauschii or the AA genome from Triticum monococcum to tetraploid wheat greatly improved root and particularly shoot growth under Zn-deficient, but not under Zn-sufficient conditions. Better growth and lesser Zn deficiency symptoms in synthetic hexaploid wheats than in tetraploid wheats were not accompanied by increases in Zn concentration per unit dry weight, but related more to the total amount of Zn per shoot, especially in the case of synthetic wheats derived from Aegilops tauschii. This result indicates higher Zn uptake capacity of synthetic wheats. The results demonstrated that the genes for high Zn efficiency from Aegilops tauschii (DD) and Triticum monococcum (AA) are expressed in the synthetic hexaploid wheats. These wheat relatives can be used as valuable sources of genes for improvement of Zn efficiency in wheat. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat

A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur, Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg⁻¹ of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg⁻¹ live chaff-inoculum and control having 0.1 g kg⁻¹ dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg⁻¹ applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg⁻¹ for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05 mg Zn kg⁻¹ soil) and medium (0.5 mg Zn kg⁻¹ soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg⁻¹ soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana     

Role of rye chromosomes in improvement of zinc efficiency in wheat and triticale

Using the disomic wheat-rye addition lines (Triticum aestivum L., cv. Holdfast-Secale cereale L., cv. King-II) and an octoploid triticale line (xTriticosecale Wittmark L. "PlutoxFakon") as well as the respective wheat and rye parents, greenhouse experiments were carried out to study the role of rye chromosomes on the severity of Zn deficiency symptoms, shoot dry matter production, Zn efficiency, shoot Zn concentration and Zn content. Plants were grown in a Zn-deficient calcareous soil with (10 mg Zn kg-1 soil) and without Zn supply. Zinc efficiency was calculated as the ratio of dry weight produced under Zn deficiency to the dry weight produced under Zn fertilization. In the experiments with addition lines, visual Zn deficiency symptoms were slight in the rye cultivar King-II, but were severe in the wheat cultivar Holdfast. The addition of rye chromosomes, particularly 1R, 2R and 7R, into Holdfast reduced the severity of deficiency symptoms. Holdfast showed higher decreases in shoot dry matter production by Zn deficiency and thus had a low Zn efficiency (53 %), while King-II was less affected by Zn deficiency and had a higher Zn efficiency (89 %). With the exception of the 3R line, all addition lines had higher Zn efficiency than their wheat parent: the 1R line had the highest Zn efficiency (80 %). In the experiment with the triticale cultivar and its parents, rye cv. Pluto and wheat cv. Fakon, Zn deficiency symptoms were absent in Pluto, slight in triticale and very severe in Fakon. Zinc efficiency was 88 % for Pluto, 73 % for triticale and 64% for Fakon. Such differences in Zn efficiency were better related to the total amount of Zn per shoot than to the amount of Zn per unit dry weight of shoot. Only in the rye cultivars, Zn efficiency was closely related with Zn concentration. Triticale was more similar to rye than wheat regarding Zn concentration and Zn accumulation per shoot under both Zn-deficient and Zn-sufficient conditions.The results presented in this study show that rye has an exceptionally high Zn efficiency, and the rye chromosomes, particularly 1R and 7R carry the genes controlling Zn efficiency. To our knowledge, the result with triticale and its rye parents is the first report showing that the genes controlling Zn efficiency in rye are transferable into wheat and can be used for development of new wheat varieties with high Zn efficiency for severely Zn-deficient conditions.     

Enhanced ototoxicity of gentamicin and salicylate caused by Mg deficiency and Zn deficiency

In rats, Mg deficiency caused a moderate hearing loss, measured by means of evoked potentials at 10 and 20 kHz, which was repaired after refeeding a normal diet. Application of 700 mg/kg salicylic acid or injection of 5×100 mg/kg gentamicin also caused a reversible hearing loss in normally fed rats. Treatment of Zn-deficient rats with salicylic acid produced a stronger although reversible hearing loss than in normally fed salicylate-treated rats. Treatment of Mg-deficient rats with gentamicin induced a strong hearing loss that was nearly complete and irreversible in 9 of 25 rats.     

Effects of dietary zinc levels on the activities of enzymes, weights of organs, and the concentrations of zinc and copper in growing rats

Zinc (Zn) is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant function, growth, and reproduction. The present study was performed to investigate the effects of three Zn levels, including Zn adequate (35.94 mg/kg, as a control), Zn deficiency (3.15 mg/kg), and Zn overload (347.50 mg/kg) in growing male rats for 6 wk. This allowed for evaluation of the effects that these Zn levels might have on body weight, organ weight, enzymes activities, and tissues concentrations of Zn and Cu. The results showed that Zn deficiency has negative effects on growth, organ weight, and biological parameters such as alkaline phosphatase (ALP) and Cu−Zn superoxide dismutase (Cu−Zn SOD) activities, whereas Zn overload played an effective role in promoting growth, improving the developments of organs and enhancing immune system. Hepatic metallothionein (MT) concentration showed an identical increase tendency in rats fed both Zn-deficient and Zn-overload diets. The actual mechanism of reduction of Cu concentration of jejunum in rats fed a Zn-overload diet might involve the modulation or inhibition of a Cu transporter protein by Zn and not by the induction of MT.     

Soil-sodicity-induced zinc deficiency in maize

Summary Maize (Zea mays L. cv. Ganga-2) plants were grown in pot culture on a loamy alluvial soil of Lucknow district (India) alkalinized to graded levels of ESP (Exchangeable Sodium Percentage) ranging from 15.5 to 55.3. Before sowing maize seeds the soil was fertilised with NPK, Fe, Mn and Cu. At and above ESP 34 Zn-deficiency symptoms first appeared at 30 days. The symptoms gradually became pronounced with increase in age and at 60 days they were found even at ESP 15.5. The severity of symptoms was related to increase in sodicity. Alkalinization of soils depressed available soil Zn and tissue Zn and increased tissue ratios of Na/Zn and P/Zn. It also decreased the total plant content of Zn, Fe, Mn, Cu and even Na. Increase in soil sodicity increased both tissue concentration and total content of P in plants upto ESP 34 beyond which it decreased it. Among different extractants, 0.1N HCl, DTPA pH 7.3 and EDTA-(NH₄)₂ CO₃ pH 8.6, for measuring available soil Zn the latter showed best correlations with soil ESP (−), tissue P (−), P/Zn ratio (−), dry matter yield (+) and tissue Zn (+). Tissue Zn was related to yield (+), tissue Na (−) and soil ESP (−). Mild, moderate, severe and very severe Zn deficiency in maize was induced by soil ESP levels, 18, 25, 33 and 45, respectively.     

Zinc deficiency-induced phytosiderophore release by the Triticaceae is not consistently expressed in solution culture

The effects of zinc (Zn) and iron (Fe) deficiencies on phytosiderophore (PS) exudation by three barley (Hordeum vulgare L.) cultivars differing in Zn efficiency were assessed using chelator-buffered nutrient solutions. A similar study was carried out with four wheat (Triticum aestivum L. and T. durum Desf.) cultivars, including the Zn-efficient Aroona and Zn-inefficient Durati. Despite severe Zn deficiency, none of the barley or wheat cultivars studied exhibited significantly elevated PS release rates, although there was significantly enhanced PS exudation under Fe deficiency. Aroona and Durati wheats were grown in a further study of the effects of phosphate (P) supply on PS release, using 100 μM KH₂PO₄ as high P, or solid hydroxyapatite as a supply of low-release P. Phytosiderophore exudation was not increased due to P treatment under control or Zn-deficient conditions, but was increased by Fe deficiency. Accumulation of P in shoots of Zn- and Fe-deficient plants was seen in both P treatments, somewhat more so under the KH₂PO₄ treatment. Zinc-efficient wheats and grasses have been previously shown to exude more PS under Zn deficiency than Zn-inefficient genotypes. We did not observe Zn-deficiency-induced PS release and were unable to replicate the results of previous researchers. The tendency for Zn deficiency to induce PS release seems to be method dependent, and we suggest that all reported instances may be explained by an induced physiological deficiency of Fe. Received: 25 October 1999 / Accepted: 3 December 1999     

Plant hydraulic lift of soil water – implications for crop production and land restoration

Zinc deficiency is a well-documented problem in food crops, causing decreased crop yields and nutritional quality. Generally, the regions in the world with Zn-deficient soils are also characterized by widespread Zn deficiency in humans. Recent estimates indicate that nearly half of world population suffers from Zn deficiency. Cereal crops play an important role in satisfying daily calorie intake in developing world, but they are inherently very low in Zn concentrations in grain, particularly when grown on Zn-deficient soils. The reliance on cereal-based diets may induce Zn deficiency-related health problems in humans, such as impairments in physical development, immune system and brain function. Among the strategies being discussed as major solution to Zn deficiency, plant breeding strategy (e.g., genetic biofortification) appears to be a most sustainable and cost-effective approach useful in improving Zn concentrations in grain. The breeding approach is, however, a long-term process requiring a substantial effort and resources. A successful breeding program for biofortifying food crops with Zn is very much dependent on the size of plant-available Zn pools in soil. In most parts of the cereal-growing areas, soils have, however, a variety of chemical and physical problems that significantly reduce availability of Zn to plant roots. Hence, the genetic capacity of the newly developed (biofortified) cultivars to absorb sufficient amount of Zn from soil and accumulate it in the grain may not be expressed to the full extent. It is, therefore, essential to have a short-term approach to improve Zn concentration in cereal grains. Application of Zn fertilizers or Zn-enriched NPK fertilizers (e.g., agronomic biofortification) offers a rapid solution to the problem, and represents useful complementary approach to on-going breeding programs. There is increasing evidence showing that foliar or combined soil+foliar application of Zn fertilizers under field conditions are highly effective and very practical way to maximize uptake and accumulation of Zn in whole wheat grain, raising concentration up to 60 mg Zn kg⁻¹. Zinc-enriched grains are also of great importance for crop productivity resulting in better seedling vigor, denser stands and higher stress tolerance on potentially Zn-deficient soils. Agronomic biofortification strategy appears to be essential in keeping sufficient amount of available Zn in soil solution and maintaining adequate Zn transport to the seeds during reproductive growth stage. Finally, agronomic biofortification is required for optimizing and ensuring the success of genetic biofortification of cereal grains with Zn. In case of greater bioavailability of the grain Zn derived from foliar applications than from soil, agronomic biofortification would be a very attractive and useful strategy in solving Zn deficiency-related health problems globally and effectively.     

Activity and subcellular distribution of protein kinase C (PKC) in muscle and brain of force-fed zinc-deficient rats

The purpose of the present study was to investigate, in force-fed rats, whether alimentary zinc (Zn) deficiency affects the activity of the Zn-metalloenzyme protein kinase C (PKC). The in vivo activity of PKC was determined by measuring the subcellular distribution of the enzyme between the cytosolic and the particulate fraction in brain and muscle. For this purpose, 24 male Sprague-Dawley rats with an average live mass of 126 g were divided into 2 groups of 12 animals each. The Zn-deficient and the control rats received a semisynthetic casein diet with a Zn content of 1.2 and 24.1 ppm, respectively. All animals were fed four times daily by gastric tube in order to ensure that the depleted animals also received adequate nutrients and to synchronize the feed intake exactly. After 12 d, the depleted rats were in a state of severe Zn deficiency, as demonstrated by a 70% lower serum Zn concentration and a 66% reduction in the serum activity of alkaline phosphatase. Neither the cytosolic nor the particulate fraction of the thigh muscle showed any difference between the depleted and the control animals as regards PKC activity/g of muscle. The specific activity of PKC/mg of protein in the cytosolic fraction of the muscle was not affected by alimentary zinc deficiency, whereas the specific activity of PKC in the particulate fraction of the muscle was reduced by a significant 10% in Zn deficiency (150±12 vs 135±14 pmol P/min/mg protein). In the brain, neither the cytosolic nor the particulate fraction revealed any difference in PKC activity/g of fresh weight or in the specific activity/mg of protein between the control and the Zn-deficient rats.     

Photosynthetic rate,chlorophyll fluorescence parameters,and lipid peroxidation of maize leaves as affected by zinc deficiency

Pot trial in greenhouse was conducted using cumulic cinnamon soil from North China to study the effects of zinc deficiency on CO₂ exchange, chlorophyll fluorescence, the intensity of lipid peroxidation, and the activity of superoxide dismutase (SOD) in leaves of maize seedlings. Zn deficiency resulted in a reduction of net photosynthetic rate and stomatal conductance to H₂O. The maximum quantum efficiency of photosystem 2 (PS2) and the PS2 activity were depressed, while the pool size of the plastoquinone molecules was not affected by Zn deficiency. The content of super oxygen anion radical (O₂ ^·−) and the intensity of lipid peroxidation as assessed by malonyldialdehyde content in Zn-deficient leaves were higher than those in Zn-sufficient leaves. The activity of SOD increased with Zn application. The adverse influence of Zn-deficiency on the light stage of photosynthesis is probably one of possible reasons for the limitation of photosynthetic capacity in maize leaves.     

Influence of alimentary zinc deficiency on the concentration of the second messengers D-myo-inositol-1,4,5-trisphosphate (IP3) and s,n-1,2-diacylglycerol (DAG) in testes and brain of force-fed rats

The phosphatidylinositol-specific phospholipase C, presumably a Zn-metalloenzyme, catalyzes the hydrolysis of phosphatidylinositol-4,5-bisphosphate to inositol-1,4,5-trisphosphate (IP₃) and s,n-1,2-diacylglycerol (DAG). The activity of phosphatidylinositol-specific phospholipase C was measured indirectly by determination of the metabolites IP₃ and DAG in Zn deficiency. For this purpose 24 male Sprague-Dawley rats with an average live mass of 117 g were divided into 2 groups of 12 animals each. The Zn-deficient and the control group received a semisynthetic casein diet with a Zn content of 1.6 ppm and 115 ppm, respectively. In order to prevent the reduced feed intake that occurs in Zn deficiency and the associated energy and protein depletion from interfering with the experimental parameters, all animals were fed four times daily by gastric tube. This made it possible to supply all animals with adequate nutrients and to synchronize the feed intake exactly. After 12 d, the depleted rats were in a severe state of Zn deficiency, as demonstrated by the reduction of Zn in the serum and the femur by 74% and 43%, respectively, and the 28% lower serum activity of alkaline phosphatase. The radioimmunologically determined concentrations of IP₃ were reduced by a significant 53% in the testes of the Zn-deficient rats (0.24 nmol IP₃/g wet wt) compared to the control animals (0.51 nmol IP₃/g wet wt), while the IP₃ concentration in the brain was not affected by the alimentary Zn supply (1.7 and 1.6 nmol IP₃/g wet wt, respectively). The DAG concentrations in the testes (474 vs 471 nmol DAG/g wet wt) and the brain (594 vs 640 nmol DAG/g wet wt), which were determined by radioenzymatic methods, showed no significant differences in relation to the alimentary Zn supply. The fact that the Zn concentration in the Zn-deficient rats was reduced only in the testes and not in the brain and that high concentrations of DAG may also result from other metabolic processes suggests that the phosphatidylinositol-specific phospholipase C in the mammalian organism is a Zn-metalloenzyme whose activity is reduced in alimentary Zn deficiency in tissues suffering Zn loss.