Effect of magnesium deficiency on the metabolism of glycosamino-glycans in rats

Magnesium deficiency in rats has significant effect on the concentration of different glycosaminoglycans in the tissues, the nature of the change being different in different tissues. Total glycosaminoglycans, chondroitin-4-sulphate + chondroitin-6-sulphate and dermatan sulphate increased in the aorta while hyaluronic acid, heparan sulphate and heparin decreased. In the liver, total glycosaminoglycans, hyaluronic acid, chondroitin-4-sulphate + 6-sulphate and heparin decreased while total glycosamino-glycans and all the glycosaminoglycan fractions increased in the heart. In the kidney, total glycosaminoglycans showed no significant alteration, hyaluronic acid and heparin decreased while chondroitin-4-sulphate + 6-sulphate increased. Activity of biosynthetic enzymesviz. glucosamine-o-phosphate isomerase and UDPG-dehydrogenase showed decrease in the liver. The concentration of 3’-phosphoadenosine 5’-phosphosulphate, activity of sulphate activating system and sulphotransferase were also similarly altered in the liver in magnesium deficiency.     

Effect of a Deficiency of Thiamine on Brain Pyruvate Dehydrogenase: Enzyme Assay by Three Different Methods

A simple and rapid method based on the NADH-linked reduction of a tetrazolium dye was described for the determination of pyruvate dehydrogenase activity in rat brain homogenates. The method (method 3) gave a value of 36.06 +/- 1.24 nmol of pyruvate utilised/min/mg of whole brain protein. This value was higher than that obtained by measurement of the rate of decarboxylation of [1-14C]pyruvate (15.10 +/- 0.88 nmol/min/mg of protein; method 1) and was comparable with the rate of transfer of acetyl groups to an arylamine (39.04 +/- 1.32 nmol/min/mg of protein; method 2). A critique of the values reported by others by different methods was given. The pyruvate dehydrogenase activity in the mitochondria isolated from rat brain was in the "active" (nonphosphorylated) form. A deficiency of thiamine in rats was produced by treatment with pyrithiamine, an antagonist of thiamine. This treatment resulted in abnormal neurological signs, such as ataxia and convulsions. The measurement of the total activity of pyruvate dehydrogenase in the brain by all three methods showed no significant change in the enzymic activity in thiamine-deficient rats after treatment with pyrithiamine. The activities of the enzyme in the brains of pair-fed animals were similar to those in the controls.     

Maternal and fetal iron accumulation in Zn-deficient and salicylate-treated rats

Nonhemoglobin Fe (non Hb−Fe) content in fetal serum and liver is much higher than in maternal serum and liver. After feeding a Zn-deficient diet to pregnant rats from d 0 to 21, non Hb−Fe content in maternal and fetal serum and liver was increased. After oral application of salicylic acid (300 mg/kg) from d 16 to 20 to normally fed and Zn-deficient dams, non Hb−Fe content in maternal and particularly in fetal serum and liver was drastically increased. In the kidney, Fe was accumulated to a small amount resulting from Zn deficiency and salicylate treatment. Fe accumulation in the liver occurred in all cell fractions, particularly in microsomes. Fe accumulation was confirmed and extended histochemically by Prussian blue staining. It is assumed that salicylate increases intestinal Fe resorption and fetal transfer of Fe. It is discussed that salicylate nephrotoxicity and its enhancement by Zn deficiency is not caused by an Fe-dependent mechanism. This work is supported by the German Research Foundation (Sfb 174)     

Enhancement of Dopamine Release In Vivo from the Rat Striatum by Dialytic Perfusion of 6R-l-erythro-5,6,7,8-Tetrahydrobiopterin

We have previously reported that intracerebroventricular administration of 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (6R-BH4), a cofactor for tyrosine hydroxylase, enhances biosynthesis of 3,4-dihydroxyphenylethylamine (dopamine) in the rat brain. In the present study, we have more precisely examined the effects of 6R-BH4 on dopamine release in vivo from the rat striatum using brain microdialysis. The amount of dopamine collected in striatal dialysates was determined using HPLC with electrochemical detection after purification with an alumina batch method. When the striatum was dialyzed with Ringer solution containing various concentrations of 6R-BH4 (0.25, 0.5, and 1.0 mM), dopamine levels in striatal dialysates increased in a concentration-dependent manner. Biopterin had little effect on dopamine levels in dialysates. The 6R-BH4-induced increase in dopamine levels in dialysates was abolished after pretreatment with tetrodotoxin (50 microM) added to the perfusion fluid, but after pretreatment with nomifensine (100 mg/kg, intraperitoneal injection), an inhibitor of dopamine uptake mechanism, a larger increase was observed. After inhibition of tyrosine hydroxylase by pretreatment with alpha-methyl-p-tyrosine (250 mg/kg, intraperitoneal injection), most of the increase persisted. These results suggest that 6R-BH4 has a dopamine-releasing action, which is not dependent on biosynthesis of dopamine.     

Neuroleptic-Induced Supersensitivity and Brain Iron: I. Iron Deficiency and Neuroleptic-Induced Dopamine D2 Receptor Supersensitivity

Previous studies have shown that nutritional iron deficiency in rats reduces brain iron content, resulting in dopamine D2 receptor subsensitivity, as indicated by a decrease in [3H]spiperone binding in caudate nucleus and in behavioral responses to apomorphine. Both phenomena can be reversed by iron supplementation. The possibility that neuroleptic-induced dopamine D2 receptor supersensitivity involves an alteration in brain iron content was investigated in nutritionally iron-deficient and control rats chronically treated with haloperidol (5 mg/kg daily for 14 or 21 days). Neuroleptic treatment was initiated either (a) concurrently with iron deficiency or (b) 2 weeks after the start of iron deficiency. The results show that dopamine D2 receptor subsensitivity, a feature of iron deficiency, is absent in haloperidol-treated, iron-deficient groups. On the contrary, these animals demonstrated biochemical and behavioral dopamine D2 receptor supersensitivity that is relatively greater than that observed with control, haloperidol-treated animals. Haloperidol (5 mg/kg daily for 21 days) as well as chlorpromazine (10 mg/kg daily for 21 days) caused a significant reduction (20-25%) in liver nonheme iron stores as compared with values in control rats. However, in iron-deficient rats, in which liver iron stores were almost totally depleted, haloperidol had no effect. The ability of chronic haloperidol treatment to prevent the reduction of dopamine D2 receptor number during iron deficiency may be associated with alteration of body iron status. Thus, less iron may result in an increase in free haloperidol available to the dopamine D2 receptor.     

Decrease in nitrate uptake and increase in proton release in zinc deficient cotton,sunflower and buckwheat plants

The effect of varied Zn supply on the pH of the nutrient solution and uptake of cations and anions was studied in cotton (Gossypium hirsutum L.), sunflower (Helianthus annuus L.) and buckwheat (Fagopyrum esculentum Moench) plants grown under controlled environmental conditions in nutrient solutions with nitrate as source of nitrogen. With the appearance of visual Zn deficiency symtoms, the pH of the nutrient solutions decreased from 6 to about 5 whereas the pH increased to about 7 when the plants were adequately supplied with Zn. In Zn deficient plants the pH decrease was associated with a shift in the cation-anion uptake ratio in favour of cation uptake. Of the major ions, uptake of Ca²⁺ and K⁺ was either not affected or only slightly lowered whereas NO₃ ^- uptake was drastically decreased in Zn deficient plants. Although the Zn nutritional status of plants hardly affected the NO₃ ^- concentrations in the plants, the leakage of NO₃ ^- from roots of Zn deficient plants into a diluted CaCl₂ solution was nearly 10 times higher than that of plants adequately supplied with Zn. In contrast to Zn deficiency, Mn deficiency in cotton plants neither affected NO₃ ^- uptake nor the pH of the nutrient solution.The results indicate that, probably as a consequence of the role of Zn in plasma membrane integrity and nitrogen metabolism, when Zn is deficient in dicotyledonous species net uptake of NO₃ ^- is particularly depressed which in turn results in an increase in cation-anion uptake ratio and a corresponding decrease in external pH. The ecological relevance of this rhizosphere acidification is discussed.     

Stem deformity inPinus radiata plantations in south-eastern Australia:

Visual symptoms of stem deformity similar to those of Cu deficiency are common inP. radiata established on fertile sites previously used for agricultural production in south-eastern Australia. In this study, Cu fertiliser was applied at rates of 0, 2, 5, 10, 20 and 50 kg ha⁻¹ to deformedP. radiata at ages 3 and 6 years. Available soil Cu and contents of Cu in the foliage increased significantly only in the younger plantation. Cu fertiliser did not affect growth nor did it improve stem form. Levels of N, Cu and Cu/N ratios in foliage of straight and deformed trees were similar. However, contents of Cu in apical buds were significantly lower in deformed trees. It was concluded that stem deformity inP. radiata as observed on these fertile pasture sites, cannot be corrected by application of Cu fertiliser. Differences in Cu levels in apical buds of straight and deformed trees suggest that Cu may still be involved in this syndrome. There was also no indication of other nutrient deficiencies that could be associated with the deformity.     

Amelioration of acid soil infertility by phosphogypsum

Amelioration of subsoil acidity requires an increase in Ca status along with a decrease in Al status in subsoil. In this study, effects of phosphogypsum (PG) on the amelioration of subsoil acidity have been evaluated, using cultivated and woodland subsoils representing Cecil, Wedowee (both Typic Hapludult) and Bladen (Typic Albaquult) series. Subsoil (0.6–0.8 m) samples were collected and treated with either PG (approximately 2 Mg ha^-1 rate), Ca(NO₃)₂ or Mg(NO₃)₂ along with an unamended control treatment. A fertile topsoil amended with NH₄NO₃ was placed on top of all treated subsoil. Top and root growth of alfalfa [Medicago sativa (L.) cv. Hunter River] and soybean [Glycine max (L.) Merr. cv. Lee] were significantly greater in PG-amended than in unamended pots of the Cecil and Wedowee soils, although most growth was observed with the Ca(NO₃)₂-amended treatment. In the Bladen soil, however, none of the amendments evoked a significant growth response in either alfalfa or soybean. The concentration of Ca in the displaced soil solution (in soils with no plants) as well as tissue levels of Ca suggest that the growth response was partly due to an improved Ca availability in both PG or Ca(NO₃)₂-treated soils. Exchangeable Al decreased in PG-amended soils. The self-liming effect of PG, which is a release of OH^- due to ligand exchange between SO₄ ^2- and OH^-, as well as a decrease in exchangeable Al in PG-amended soil is greater in predominantly kaolinitic Cecil and Wedowee soils than in smectitic Bladen soil. As a result, significant growth response to PG amendment was observed in the Cecil and Wedowee soils, but not in the Bladen soil.     

啤酒酵母呼吸缺陷型诱变形成机制初探

本文以两株不同的啤酒酵母(S.cerevisiae)作出发菌株,用溴化乙锭(10—100μg/ml)作诱变剂,诱变呼吸缺陷型。发现在非生长条件下,EB诱变呼吸缺陷型过程中出现回复现象。这一现象可被咖啡碱有一定程度的抑制,而在生长条件下EB诱变过程中未发现此现象。但当用KCN处理时,则得到了类似于非生长条件下的诱变结果。因而,推测呼吸缺陷型形成过程中可能存在一中间态过程[ρ~-]~*。呼吸缺陷型的形成过程可用ρ~ [ρ~-]~*→ρ~-表示。这是一动态过程。加入一定量的放线菌酮、氯霉素处理时,对诱变动力学曲线没有发现有影响,但培养酵母所用葡萄糖浓度不同时,对其诱变结果有一定的影响。     

Effect of iron deficiency on ferredoxin levels in Anabaena variabilis PCC 6309

Cultures of the nitrogen-fixing cyanobacterium Anabaena variabilis PCC 6309 were grown under several iron concentrations, and changes in growth rates and chlorophyll and phycocyanin concentrations were determined. The total amount of ferredoxin present in the cells was found to be dependent on the concentration of iron in the media, as was the pattern distribution of the two different forms of the iron-sulfur protein described in this organism. Flavodoxin was not found to be present in these cells even when they were grown in the absence of added iron, indicating that this flavoprotein does not replace ferredoxin in this particular strain.