Nutrients in the shadow-nutrients of substance

While the dietary importance of proteins, essential fatty acids, vitamins and trace elements has been well recognised, the role of shadow nutrients, a class of metabolites, which are biosynthesized in the body and serve vital functions, such as lipoic acid, choline, inositol, taurine and carnitine, has not been adequately appreciated. There are reasons to believe that during infancy and in ageing, biosynthesis of these metabolites may be limited. The objective of this review is to highlight the essentiality of these nutrients and the need for their supplementation in the diets of infants and in elderly people. Provision of shadow nutrients where the necessary biosynthetic machinery might not have developed to full stature or might have slowed down, is a new concept in nutrition which needs attention.     

Inhibition of methanogenesis and its reversal during biogas formation from cattle manure

The composition of volatile fatty acids in the biogas digester based on cattle manure as substrate and stabilised at 25°C showed that it contained 87–88% branched chain fatty acids, comprising of isobutyric and isovaleric acids, in comparison to 38 % observed in the digester operating at 35°C. Mixed cellulolytic cultures equilibrated at 25°C (C-25) and 35‡C (C-35) showed similar properties, but rates of hydrolysis were three times higher than that observed in a standard biogas digester. The proportion of isobutyric and isovaleric were drastically reduced when C-25 was grown with glucose or filter paper as substrates. The volatile fatty acids recovered from C-25 (at 25°C) inhibited growth of methanogens on acetate, whereas that from C-35 was not inhibitory. The inhibitory effects were due to the branched chain fatty acids and were observed with isobutyric acid at concentrations as low as 50 ppm. Addition of another micro-organismRhodotorula selected for growth on isobutyric completely reversed this inhibition. Results indicate that the aceticlastic methanogens are very sensitive to inhibition by branched chain fatty acids and reduction in methane formation in biogas digester at lower temperature may be due to this effect.     

Breeding for resistance to downy mildews and stalk rots in maize

Summary The present review includes information on distribution, symptoms, inoculation techniques, disease rating, sources of resistance, genetics of resistance, breeding approaches for resistance, and the present status of resistance breeding with respect to Sclerophthora and Peronosclerospora downy mildews and Erwinia, Cephalosporium and Fusarium stalk rots. Some suggestions highlighting research gaps pertinent to future breeding strategies are mentioned.Publication No. 2993, Experiment Station, GB Pant University of Agriculture and Technology, Pantnagar, India     

Cyclic nucleotide phosphodiesterases from rat anterior pituitary. Characterization of multiple forms and regulation by protein activator and Ca+.

Phosphodiesterase activities for adenosine and guanosine 3':5'-monophosphates (cyclic AMP and cyclic GMP) were demonstrated in particulate and soluble fractions of rat anterior pituitary gland. Both fractions contained higher activity for cyclic GMP hydrolysis than that for cyclic AMP hydrolysis when these activities were assayed at subsaturating substrate concentrations. Addition of protein activator and CaCl2 to either whole homogenate, particulate or supernatant fraction stimulated both cyclic AMP and cyclic GMP phosphadiesterase activities. Almost 80% of cyclic AMP and 90% of cyclic GMP hydrolyzing activities were localized in soluble fraction. Particulate-bound cyclic nucleotide phosphodiesterase activity was completely solubilized with 1% Triton X-100. Detergent-dispersed particulate and soluble enzymes were compared with respect to Ca2+ and activator requirements and gel filtration profiles. Particulate, soluble and partially purified phosphodiesterase activities were also characterized in relation to divalent cation requirements, kinetic behavior and effects of Ca2+, activator and ethyleneglycol-bis-(2-aminoethyl)-N,N'-tetraacetic acid. Gel filtration of either sonicated whole homogenate or the 10500 X g supernatant fraction showed a single peak of activity, which hydrolyzed both cyclic AMP and cyclic GMP and was dependent upon Ca2+ and activator for maximum activity. Partially purified enzyme was inhibited by 1-methyl-3-isobutylxanthine and papaverine with the concentration of inhibitor giving 50% inhibition at 0.4 muM substrate being 20 muM and 24 muM for cyclic AMP and 7 muM and 10 muM for cyclic GMP, respectively. Theophylline, caffeine and theobromine were less effective. The rat anterior pituitary also contained a protein activator which stimulated both pituitary cyclic nucleotide phosphodiesterase(s) as well as activator-deficient brain cyclic GMP and cyclic AMP phosphodiesterases. Chromatography of the sonicated pituitary extract on DEAE-cellulose column chromatography resolved the phosphodiesterase into two fractions. Both enzyme fractions hydrolyzed cyclic AMP and cyclic GMP and had comparable apparent Km values for the two nucleotides. Hydrolysis of cyclic GMP and cyclic AMP by fraction II enzyme was stimulated 6--7-fold by both pituitary and brain activator in the presence of micromolar concentrations of Ca2+.     

Aliphatic compounds from Costus speciosus roots

Two new compounds G and H isolated from the roots of Costus speciosus have been characterized as 8-hydroxytriacontan-25-one and Me tritriacontanoat     

Receptor-mediated gonadotropin action in the ovary. Action of cytoskeletal element-disrupting agents on gonadotropin-induced steroidogenesis in rat luteal cells.

The role of the cellular cytoskeletal system of microtubules and microfilaments on gonadotropin-stimulated progesterone production by isolated rat luteal cells has been investigated. Exposure of luteal cells to human choriogonadotropin resulted in a stimulation of cyclic AMP (4-7-fold) and progesterone (3-4-fold) responses.l Incubation of cells with the microfilament modifier cytochalasin B inhibited the gonadotropin-induced steroidogenesis in a dose- and time-dependent manner. The effect of cytochalasin B on basal production of steroid was less pronounced. Cytochalasin B also inhibited the accumulation of progesterone in response to lutropin, cholera enterotoxin, dibutyryl cyclic AMP and 8-bromo cyclic AMP. The inhibition of steroidogenesis by cytochalasin B was not due to (a) inhibition of 125I-labelled human choriogonadotropin binding to luteal cells, (b) inhibition of gonadotropin-stimulated cyclic AMP formation or (c) a general cytotoxic effect and/or inhibition of protein biosynthesis. Cytochalasin D, like cytochalasin B, inhibited gonadotropin- and 8-bromo cyclic AMP-stimulated steroidogenesis. Although cytochalasin B also blocked the transport of 3-O-methyl-glucose into luteal cells, cytochalasin D was without such an effect. Increasing glucose concentration in the medium, or using pyruvate as an alternative energy source, failed to reverse the inhibitory effect of cytochalasin B. The anti-microtubular agent colchicine failed to modulate synthesis and release of progesterone by luteal cells in response to human choriogonadotropin. These studies suggest that the cellular microfilaments may be involved in the regulation of gonadotropin-induced steroidogenesis. In contrast, microtubules appear to be not directly involved in this process.     

Studies on the chemical modification of potato (Solanum tuberosum) lectin and its effect on haemagglutinating activity

1. Modification of potato (Solanum tuberosum) lectin with acetic anhydride blocked 5.1 amino and 2.7 tyrosyl groups per molecule of lectin and decreased the haemagglutinating activity of the lectin. De-O-acetylation regenerated 2.0 of the tyrosyl groups and resulted in a recovery of activity. 2. Modification with citraconic anhydride or cyclohexane-1,2-dione did not greatly affect activity, although modification of amino and arginyl groups could be demonstrated. 3. Treatment with tetranitromethane nitrated 3.7 tyrosine residues per molecule of lectin with concomitant loss of activity. The presence of 0.1m-NN′N″-triacetylchitotriose (a potent inhibitor of the lectin) in the reaction medium protected all the tyrosyl residues from nitration and the lectin was fully active. 4. Modification of tryptophyl groups with 2-hydroxy-5-nitrobenzyl bromide and 2,3-dioxoindoline-5-sulphonic acid modified 0.9 and 2.6 residues per molecule of lectin respectively with a loss of activity in each case. Reaction of potato lectin with 2,3-dioxoindoline-5-sulphonic acid in the presence of inhibitor protected 2.4 residues of tryptophan from the reagent. Loss of haemagglutination activity was prevented under these conditions. 5. Reaction of carboxy groups, activated with carbodi-imide, with α-aminobutyric acid methyl ester led to the incorporation of 5.3 residues of the ester per molecule of lectin. Presence of inhibitor in this case, although protecting activity, did not prevent modification of carboxy groups; in fact an increase in the number of modified residues was seen. This effect could be imitated by performing the reaction in 8m-urea. In both cases the number of carboxy groups modified was close to the total number of free carboxy groups as determined by the method of Hoare & Koshland [(1967) J. Biol. Chem. 242, 2447–2453]. Guanidination of lysine residues after carboxy-group modification gave less homoarginine than did the unmodified lectin under the same conditions, suggesting the formation of intramolecular cross-links during carbodi-imide activation. 6. It is suggested from the results presented that amino, arginyl, methionyl, histidyl and carboxyl groups are not involved in the activity of the lectin and that tyrosyl and tryptophyl groups are very closely involved. These findings are similar to those reported for other proteins that bind N-acetylglucosamine oligomers and also fit the general trend in other lectins.     

Subsoil gravel horizon and maize root growth

Summary A series of factoral experiments involving the effects of gravel concentration in the subsoil horizon, the effect of inter-gravel bulk density, the depth of the surface soil above the gravel horizon and the interaction between soil moisture regime and gravel concentration, on growth and development of maize roots were conducted in the greenhouse. Increasing sub soil gravel concentration decreased the total porosity and the available waterholding capacity. Though the root growth of maize seedlings was adversely affected by gravel concentration above 20 per cent, lower concentration of gravels had a beneficial effect on roots. The root development and the leaf concentration of N, P and K improved with increasing depth of surface soil above the gravel horizon. The symptoms of mechanical impedance, such as thickening of root tips and profuse branching behind the tip were commonly observed on the root axis penetrating the gravelly horizon. re]19750916     

Differential reduction of morphine-withdrawal body shakes by butaclamol enantiomers

Rats withdrawn from continuous morphine infusion showed reliable occurrence of withdrawal body shakes. This sign of narcotic withdrawal was inhibited by the neuroleptic drug, (+) butaclamol. (?) Butaclamol was inactive. (+) Butaclamol activity was not antagonized by naloxone (5 mg/kg). The anti-withdrawal mechanism of (+) butaclamol is discussed in terms of effects on dopamine and narcotic receptors.The butyrophenone neuroleptic, haloperidol, has been used successfully to reduce signs of narcotic withdrawal in laboratory animals (1–4) and human addicts (5). Other neuroleptics of the butyrophenone type also show anti-withdrawal action (6, 7). The mechanism of action of these neuroleptics in blocking narcotic withdrawal is not understood. Butaclamol is a new neuroleptic drug that is available in two enantiomers and only (+) butaclamol possesses neuroleptic activity (8–10). Because of its demonstrated stereo-specificity in producing its pharmacological action, we employed this drug to establish specificity of action of neuroleptics in blocking narcotic withdrawal.     

The mevalonate pathway in the bloodstream form of Trypanosoma brucei. Identification of dolichols containing 11 and 12 isoprene residues

The major surface antigen of the bloodstream form of Trypanosoma brucei, the variant surface glycoprotein, is attached to the plasma membrane via a glycosylphosphatidylinositol anchor. The biosynthesis of the glycosylphosphatidylinositol anchor, as well as the assembly of the asparagine-linked oligosaccharide chains found on the variant surface glycoproteins, involves polyisoprenoid lipids that act as sugar carriers. Preliminary observations (Menon, A.K., Schwarz, R.T., Mayor, and Cross, G.A.M. (1990) J. Biol. Chem. 265, 9033-9042) suggested that the sugar carriers in T. brucei were short-chain polyisoprenoids containing substantially fewer isoprene residues than polyisoprenols in mammalian cells. In this paper we describe metabolic labeling experiments with [3H]mevalonate, as well as chromatographic and mass spectrometric analyses of products of the mevalonate pathway in T. brucei. We report that cells of the bloodstream form of T. brucei contain a limited spectrum of short chain dolichols and dolichol phosphates (11 and 12 isoprene residues). The total dolichol content was estimated to be 0.28 nmol/10(9) cells; the dolichyl phosphate content was 0.07 nmol/10(9) cells. The same spectrum of dolichol chain lengths was also found in a polar lipid that could be labeled with [3H]mevalonate, [3H]glucosamine, and [3H]mannose, and which was characterized as Man5GlcNAc2-PP-dolichol. The most abundant product of the mevalonate pathway identified in T. brucei was cholesterol (140 nmol/10(9) cells). Ubiquinone (0.09 nmol/10(9) cells) with a solanesol side chain was also identified.