Functional mutants of Azospirillum brasilense elicit beneficial physiological and metabolic responses in Zea mays contributing to increased host iron assimilation.

Iron (Fe), an essential element for plant growth, is abundant in soil but with low bioavailability. Thus, plants developed specialized mechanisms to sequester the element. Beneficial microbes have recently become a favored method to promote plant growth through increased uptake of essential micronutrients, like Fe, yet little is known of their mechanisms of action. Functional mutants of the epiphytic bacterium Azospirillum brasilense, a prolific grass-root colonizer, were used to examine mechanisms for promoting iron uptake in Zea mays. Mutants included HM053, FP10, and ipdC, which have varying capacities for biological nitrogen fixation and production of the plant hormone auxin. Using radioactive iron-59 tracing and inductively coupled plasma mass spectrometry, we documented significant differences in host uptake of Fe2+/3+ correlating with mutant biological function. Radioactive carbon-11, administered to plants as 11CO2, provided insights into shifts in host usage of 'new' carbon resources in the presence of these beneficial microbes. Of the mutants examined, HM053 exhibited the greatest influence on host Fe uptake with increased plant allocation of 11C-resources to roots where they were transformed and exuded as 11C-acidic substrates to aid in Fe-chelation, and increased C-11 partitioning into citric acid, nicotianamine and histidine to aid in the in situ translocation of Fe once assimilated.

Assessing microleakage of class V resin composite restorations after Er:YAG laser and bur preparation.

BACKGROUND AND OBJECTIVE: This study aimed to evaluate the extent of microleakage in cavities prepared with bur and Er:YAG laser, hybridized with different bonding systems. STUDY DESIGN: Sixty bovine teeth were randomly divided into six groups (n = 10): (G1) Diamond bur + Single Bond; (G2) Diamond bur + AdheSE; (G3) Diamond bur + Clearfil SE Bond; (G4) Er:YAG (250 mJ, 4 Hz, 80.6 J/cm(2)) + Single Bond; (G5)Er:YAG + AdheSE, and (G6) Er:YAG + Clearfil. Cavities were restored with a micro-hybrid composite resin. After thermocycling, the specimens were stained with 2% methylene blue solution and sectioned in the mesiodistal direction. Dye penetration was scored based upon the extent of the dye using a light stereoscope. RESULTS: The Kruskal-Wallis and Mann-Whitney test revealed no statistically significant differences between the method of preparation (diamond bur and laser). However, statistical differences were found between the adhesives tested. CONCLUSION: Based on the results of this study, Er:YAG laser confirmed to be as effective as the conventional methods for preparing adhesive restorations.

An in-progress research report of perceptual-cognitive development of young black children in three cultures.

This paper examines a study of perceptual-cognitive development among black children from three cultures. The study investigates patterns of perceptual and cognitive functioning as a transaction among developmental, genetic, environmental, cultural, and child-rearing variables. The samples consisted of four and eight year olds from three distinct groups: (1) white and black middle socio-economic status (SES) children from the US; (2) lower and middle SES children from St. Kitts in the Caribbean; and (3) middle SES children from Nigeria. The research paradigm permits a cross-cultural comparison of three samples of middle-class, urban, English-speaking, black children in relation to six areas of perceptual-cognitive development, four anthropometric, and three physiological measures. Because of the inclusion of a white sample, the interactions of SES, race, culture, nutritional status, proximity to the equator, and physical growth and development can be correlated with the performance of black children on perceptual-cognitive tasks. Results of data analyzed thus far are reported and implications are discussed.

Secretory IgA in the serum of infants with obstructive jaundice.

The liver is capable of transporting IgA from the plasma to bile in several experimental animals. After bile duct ligation, SIgA and free secretory component accumulate in the serum of these animals. In the present study, SIgA was found in the serum of all infants with extrahepatic biliary obstruction, and in 75% of those with intrahepatic cholestasis, but in only one of seven age-matched infants without hepatobiliary disease. Infants with EHBO had significantly higher serum levels of secretory IgA and total IgA than in normal infants or patients with IHC. This result suggests that the human liver is involved in SIgA metabolism and that the elevated serum IgA levels in infants with liver disease are caused by bile duct obstruction or proliferation. Quantitation of SIgA in serum may help to differentiate major categories of obstructive jaundice in infancy. The concentration of SIgA in serum was indicative of the site of obstruction in 12 of 19 infants with hepatobiliary disease.

Prolidase deficiency: report of a second case with quantitation of the excessively excreted amino acids.

The second documented case of prolidase deficiency is presented. Clinical manifestations include chronic otitis media and sinusitis, dermatitis, and splenomegaly. Prolidase is undetectable in the white blood cells of the patient and near or less than the lower range of normal in each parent. The peptide chromatographic pattern of the urine is similar to that of the previously reported patient with prolidase deficiency. The quantity of amino acids excreted in urine per 24 hours is at least three times that of the upper range of normal (of these same amino acids) for the patients age group. More than 80% of the total amino acids excreted are in peptide form. The proline-to-hydroxyproline ratio suggests that the dipeptides are the catabolic products of other proteins in addition to collagen.

Enterocolitis in low-birth-weight infants associated with milk and soy protein intolerance.

Two low-birth-weight infants developed a syndrome of vomitting, distension, septic appearance, and bloody diarrhea. Both infants developed symptoms after ingestion of cow milk-based formula initially, and, later, soy-based formulas. These symptoms resolved with intravenous fluids and alimentation. Vomiting, diarrhea, melena, and polymorphonuclear leukocytosis recurred with reintroduction of either milk- or soy-based formulas. This sensitivity persisted throughout the neonatal period and was still present at seven to eight months of age. It appears from these data that intolerance to whole protein formulas can cause a syndrome similar clinically to neonatal necrotizing enterocolitis.