SynopsisConformational change of histone IV, induced by phosphate, have been investigated by observing the intrinsic fluorescence of tyrosine residues and circular dichroism (CD). There is a fast conformational change upon the addition of phosphate, followed by a slow process with time constants in the range of minutes to hours depending upon both the phosphate and histone concentrations. The CD results indicate a-helix formation in the fast process, and @-sheet formation in the slow one, although other secondary and tertiary structural changes also may occur. The histone concentration dependence of the fast process is consistent with dimerization. Divalent phosphate is about ten times more effective than monovalent phosphate in inducing conformational changes. All of the changes are reversible.of New York,

Vasoconstriction has been associated with several symptoms of fescue toxicosis thought to be alkaloid induced. Lysergic acid, an ergot alkaloid, has been proposed as a toxic component of endophyte-infected tall fescue. The objective of this study was to examine the vasoconstrictive potential of D-lysergic acid using a bovine lateral (cranial branch) saphenous vein bioassay. Before testing lysergic acid, validation of the bovine lateral saphenous vein bioassay for use with a multimyograph apparatus was conducted using a dose-response to norepinephrine to evaluate the effects of limb of origin (right vs. left) and overnight storage on vessel contractile response. Segments (2 to 3 cm) of the cranial branch of the lateral saphenous vein were collected from healthy mixed breed cattle (n = 12 and n = 7 for the lysergic acid and norepinephrine experiments, respectively) at local abattoirs. Tissue was placed in modified Krebs-Henseleit, oxygenated buffer and kept on ice or stored at 2 to 8 degrees C until used. Veins were trimmed of excess fat and connective tissue, sliced into 2- to 3-mm sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O2, 5% CO2; pH = 7.4; 37 degrees C). Tissue was allowed to equilibrate at 1 g of tension for 90 min before initiation of treatment additions. Increasing doses of norepinephrine (1 x 10(-8) to 5 x 10(-4) M) or lysergic acid (1 x 10(-11) to 1 x 10(-4) M) were administered every 15 min after buffer replacement. Data were normalized as a percentage of the contractile response induced by a reference dose of norepinephrine. Veins from both left and right limbs demonstrated contractions in a dose-dependent manner (P < 0.01) but did not differ between limbs. There were no differences in dose-response to norepinephrine between tissue tested the day of dissection and tissue tested 24 h later. Exposure of vein segments to increasing concentrations of lysergic acid did not result in an appreciable contractile response until the addition of 1 x 10(-4) M lysergic acid (15.6 +/- 2.3% of the 1 x 10(-4) M norepinephrine response). These data indicate that only highly elevated concentrations of lysergic acid result in vasoconstriction. Thus, in relation to the symptoms associated with vasoconstriction, lysergic acid may only play a minor role in the manifestation of fescue toxicosis.

Abstract. The varieties of perennial ryegrass (Lolium perenne) infected with the endophytic fungus Neotiphodium lolii contain several classes of toxic alkaloids, including ergopeptide alkaloids and lolitrem alkaloids. Lolitrem B, a potent tremorgen, is generally considered to be the predominant alkaloid in endophyte-infected perennial ryegrass. Ergovaline, a vasoconstrictor normally associated with endophyte-infected tall fescue (Festuca arudinacea), is also present in endophyte infected perennial ryegrass. Clinical signs of animals ingesting endophyte-infected perennial ryegrass are consistent with the presence of lolitrem B. However, clinical signs normally associated with ergovaline poisoning are not usually observed in animals ingesting endophyte-infected perennial ryegrass. A survey was conducted to quantitate both lolitrem B and ergovaline in 459 perennial ryegrass straw samples received at the Oregon State University College of Veterinary Medicine. Samples were analyzed for each alkaloid using separate high-performance liquid chromatography analyses. A strong positive correlation between the 2 alkaloids (r 2 ϭ 0.7335) was observed, especially in the samples containing Ͻ3,000 ppb (ng/g) lolitrem B. The threshold levels above which clinical signs typically occur are 2,000 ppb lolitrem B and 300-400 ppb ergovaline. All of the samples analyzed contained Ͻ425 ppb ergovaline.

Synthetic vitamin E, all-rac-alpha-tocopherol, contains eight different stereoisomers, only one of which, RRR-alpha-tocopherol, occurs naturally. The objective of this investigation was to evaluate the relative abilities of these two vitamin E forms to enrich piglet tissues when fed as alpha-tocopheryl acetates to sows during pregnancy and lactation. alpha-Tocopherol delivery to fetuses and to suckling piglets was monitored by feeding 150 mg each of d(3)-RRR-alpha- and d(6)-all-rac-alpha-tocopheryl acetate to three pregnant sows daily from 7 d before to 7 d after giving birth. Labeled and unlabeled vitamin E concentration ratios were measured in sow plasma and milk, and in piglet (n = 9) plasma and tissues at birth, 7 and 21 d. At birth, despite elevated sow plasma deuterated alpha-tocopherol concentrations, no labeled alpha-tocopherol was detected in piglet plasma or tissues. Sow plasma and milk d(3)-alpha- to d(6)-alpha-tocopherol concentrations were 2:1, leading to a 2:1 ratio in suckling piglet plasma and tissues. In piglets at d 7 compared with birth, most tissues contained a 10-fold increase in total alpha-tocopherol; the highest deuterated vitamin E concentrations were in the liver, followed by the lung, heart, kidney, muscle, intestine and brain. In conclusion, pigs discriminate between RRR- and all-rac-alpha-tocopherol with a preference for RRR-alpha-tocopherol; thus, the official bioequivalence ratio of 1.36:1 RRR- to all-rac-alpha-tocopherol is underestimated. After initiation of suckling, piglet plasma and tissues demonstrated a dramatic increase in vitamin E concentrations, emphasizing the limited placental vitamin E transfer and the importance of milk for enhancing the vitamin E status of the newborn.

Neurological disorders have been reported from parts of Africa with protein-deficient populations and attributed to cyanide (CN-) exposure from prolonged dietary use of cassava, a cyanophoric plant. Cyanide is normally metabolized to thiocyanate (SCN-) by the sulfur-dependent enzyme rhodanese. However, in protein-deficient subjects where sulfur amino acids (SAA) are low, CN may conceivably be converted to cyanate (OCN-), which is known to cause neurodegenerative disease in humans and animals. This study investigates the fate of potassium cyanide administered orally to rats maintained for up to 4 weeks on either a balanced diet (BD) or a diet lacking the SAAs, L-cystine and L-methionine. In both groups, there was a time-dependent increase in plasma cyanate, with exponential OCN- increases in SAA-deficient rats. A strongly positive linear relationship between blood CN- and plasma OCN- concentrations was observed in these animals. These data are consistent with the hypothesis that cyanate is an important mediator of chronic cyanide neurotoxicity during protein-calorie deficiency. The potential role of thiocyanate in cassava-associated konzo is discussed in relationship to the etiology of the comparable pattern of motor-system disease (spastic paraparesis) seen in lathyrism.