Abnormal concentrations of B vitamins and amino acids in plasma, bile, and liver of chicks with aflatoxicosis.

Graded levels of aflatoxin fed to broiler chickens for 3 weeks decreased the levels of most B vitamins in plasma, bile, and liver and decreased all free and hydrolyzed amino acids from peptides in plasma. The levels of thiamine, riboflavin, vitamin B6, pantothenic acid, and choline decreased by more than 60% in bile; vitamin B6, pantothenic acid, and choline decreased by more than 49% in plasma; thiamine, vitamin B6, pantothenic acid, choline, folate, and niacin decreased by more than 19% in liver; and only bile and plasma levels of folate increased (78 and 12%, respectively) with a dietary level of 5 microgram of aflatoxin per g of feed. Plasma levels of cystine and cysteine, methionine, threonine, serine, and aspartic acid decreased by more than 37%, whereas valine, lysine, leucine, histidine, hydroxyproline, and alanine decreased by more than 9% with 2.5 microgram of aflatoxin per g of feed. The data suggest that aflatoxin interferes with the metabolism of B vitamins and amino acids in chicks. However, these changes may be measuring the effects of aflatoxin-induced hepatic necrosis.     

Variation and taxonomy of Pyxidanthera (Diapensiaceae)

Brittonia - Morphological and ecological studies of seven populations ofPyxidanthera barbulata Michx. in North and South Carolina indicate that the variation among populations is clinal and...     

A family-based approach to preventing excessive weight gain

Objective: Preventing weight gain in adults and excessive weight gain in children is a high priority. We evaluated the ability of a family‐based program aimed at increasing steps and cereal consumption (for breakfast and snacks) to reduce weight gain in children and adults. Research Methods and Procedures: Families (n = 105) with at least one 8‐ to 12‐year‐old child who was at‐risk‐for‐overweight or overweight (designated as the target child) were recruited for the study. Eighty‐two families were randomly assigned to receive the family‐based intervention and 23 families to the control condition. The 13‐week intervention consisted of specific increases in daily steps (an additional 2000 steps/d) and consumption of 2 servings/d of ready‐to‐eat cereal. Results: The intervention was successful in increasing walking (steps) and cereal consumption. The intervention had positive, significant effects on percentage BMI‐for‐age and percentage body fat for target children and weight, BMI, and percentage body fat for parents. On further analysis, the positive effects of the intervention were seen largely in target girls and moms, rather than in target boys and dads. Discussion: This family‐based weight gain prevention program based on small changes holds promise for reducing excessive weight gain in families and especially in growing overweight children.     

Cyclic nucleotide phosphodiesterases in the cricket, Acheta domesticus.

Exceptionally high levels of guanosine 3'-5'-cyclic monophosphate (cyclic GMP) in the accessory reproductive gland of the male house cricket, Acheta domesticus, led to an investigation of cyclic nucleotide phosphodiesterase (EC 3.1.4.--) as a possible regulatory enzyme. Cricket cyclic nucleotide phosphodiesterase activity with cyclic GMP or cyclic AMP as substrate had a pH optimum around 9.0, required Mg2+ or Mn2+ for maximal activity, and was inhibited by EDTA and methylxanthines. Cyclic GMP phosphodiesterase occurred mainly in the soluble fraction of homogenates of accessory glands or whole crickets, but cyclic AMP phosphodiesterase in the accessory gland was primarily particulate. Kinetic analysis indicated three forms of cyclic GMP phosphodiesterase, with Km values at 2.9 muM, 71 muM and 1.5 mM. Chromatography of whole cricket or accessory gland extracts on DEAE cellulose gave an initial peak having comparable activity with either cyclic GMP or cyclic AMP, and a second peak specific for cyclic AMP. There were no appreciable changes in the specific activity or kinetic properties of accessory gland cyclic GMP phosphodiesterase during a developmental period over which cyclic GMP levels rise more than 500-fold. Thus, the accumulation of cyclic GMP in the accessory gland is probably not associated with concomitant developmental modulation of phosphodiesterase activity.     

Expression of the high capacity calcium-binding domain of calreticulin increases bioavailable calcium stores in plants

Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca²⁺-transport and storage pathways that include Ca²⁺ buffering proteins in the lumen of intracellular compartments. To date, most research has focused on the role of transporters in regulating cytosolic calcium. We used a reverse genetics approach to modulate calcium stores in the lumen of the endoplasmic reticulum. Our goals were two-fold: to use the low affinity, high capacity Ca²⁺ binding characteristics of the C-domain of calreticulin to selectively increase Ca²⁺ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. The C-domain of calreticulin is a highly acidic region that binds 20–50 moles of Ca²⁺ per mole of protein and has been shown to be the major site of Ca²⁺ storage within the endoplasmic reticulum of plant cells. A 377-bp fragment encoding the C-domain and ER retention signal from the maize calreticulin gene was fused to a gene for the green fluorescent protein and expressed in Arabidopsis under the control of a heat shock promoter. Following induction on normal medium, the C-domain transformants showed delayed loss of chlorophyll after transfer to calcium depleted medium when compared to seedlings transformed with green fluorescent protein alone. Total calcium measurements showed a 9–35% increase for induced C-domain transformants compared to controls. The data suggest that ectopic expression of the calreticulin C-domain increases Ca²⁺ stores, and that this Ca²⁺ reserve can be used by the plant in times of stress.     

Localization of retinol-binding protein messenger RNA in the rat kidney and in perinephric fat tissue

The cellular localization of retinol-binding protein (RBP) messenger RNA (mRNA) in the kidney, and the developmental pattern of the renal expression of the RBP gene, were studied in the Sprague-Dawley rat. In situ hybridization studies were conducted with single-stranded cRNA probes, using sections of adult and young rat kidneys. These studies revealed specific localization of RBP mRNA in the outer stripe of the medulla, specifically localized in the S3 segment of the proximal tubules. Northern blot analysis demonstrated that RBP mRNA was not detectable in the kidney before birth or during the first week postpartum, but was clearly detected by the end of the second week of age. No RBP mRNA was observed in the kidney by in situ hybridization at 12 days of age. At 26 days of age, however, RBP mRNA was clearly detected by the in situ hybridization technique, localized in the same anatomic region as that observed in the adult kidney. Transthyretin mRNA was not detected in the adult kidney. Previous studies have shown that immunoreactive RBP is localized in the convoluted segment of the proximal tubules of the rat kidney. The present results demonstrate that RBP mRNA in the kidney is localized in an anatomic region (the S3 segment of the proximal tubules) different from that of immunoreactive RBP. In addition, an intense RBP mRNA hybridization signal was detected in the perinephric fat tissue of 26- and 40-day-old and adult rats. Further analysis of RNA from epididymal fat showed a level of RBP mRNA approximately 20% of that of liver. The function of RBP synthesized in the kidney and adipose tissue remains to be determined. We have previously hypothesized that RBP synthesized in extrahepatic tissue may function in the recycling of retinol back to the liver or to other target tissues.