Significance of Polyamines for Flowering in Spirodela punctata

Spirodela punctata strain O 5, a quantitative long-day plant,flowers only when ethylene-diamine-di-o-hydroxyphenylaceticacid (EDDHA) or salicylic acid was added to the nutrient medium[Scharfetter et al. (1978) Z. Pflanzenphysiol. 87: 445]. Undersuch conditions, cyclohexylamine and methylglyoxal-bis(guanylhydrazone)(both blockers of polyamine synthesis) inhibited flowering withoutsignificant effects on vegetative growth. Supply of spermidineabolished completely the inhibitor effects, but cannot replacethe EDDHA effect on flowering. ¹Dedicated to Prof. O. H. Volk, Wurzburg, on his 85th birthday. ²Present address: Facultad de Ciencias Forestales, UniversidadAutónoma de Nuevo León. Ap. Post. 41, 67700 Linares,Nuevo León, México. (Received October 19, 1988; Accepted February 3, 1989)     

Influence of maize root mucilage on soil aggregate stability

This study was undertaken to determine the effects of root exudates on soil aggregate stability. Root mucilage was collected from two-month old maize plants (Zea mays L.) Mucilage and glucose solutions were added at a rate of 2.45 g C kg⁻¹ dry soil to silty clay and silt loam soils. Amended soils, placed in serum flasks, were incubated for 42 d with a drying-wetting cycle after 21 d. Evolved CO₂ was measured periodically as well as the water-stable aggregates and soluble sugar and polysaccharide content of the soil. In mucilage-amended soils CO₂ evolution started with a lag phase of 2–3 days, which was not observed in glucose-amended soils. There was then a sharp increase in evolved CO₂ up to day 7. During the second incubation period there were only small differences in evolved C between treatments. Incorporation of mucilage in both soils resulted in a spectacular and immediate increase in soil aggregate stability. Thereafter, the percent of water-stable aggregates quickly decreased parallel to microbial degradation. On completion of the incubation, aggregate stability in the silty clay soil was still significantly higher in the presence of mucilage than in the control. This work supports the assumption that freshly released mucilage is able to stick very rapidly to soil particles and may protect the newly formed aggregates against water destruction. On the silty clay, microbial activity contributes to a stabilization of these established organo-mineral bounds.     

Purification and partial characterization of the soluble low Km 5'-nucleotidase from human seminal plasma

Soluble low Km 5'-nucleotidase from human seminal plasma has been purified to homogeneity by one affinity and two gel-filtration chromatographic steps. The pure enzyme had a specific activity of 2000 nmol min-1 mg-1. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of purified low Km 5'-nucleotidase revealed a single polypeptide band of 40 +/- 7 kDa and a tetrameric structure of 160 +/- 10 kDa has been proposed for the native enzyme. The kinetic properties of low Km 5'-nucleotidase have been determined and rather unique characteristics have been found for this soluble low Km 5'-nucleotidase: the substrate efficiency was slightly higher for IMP with an optimum pH at 7.5; the enzyme showed an absolute dependence on Mg2+ ions. Ca2+ could replace Mg2+ ions for activity while other divalent cations could not substitute for Mg2+; the enzymes were equally activated by ATP and ADP up to 0.1 mM concentrations. At higher concentrations up to 1 mM, ADP was still an activator while ATP caused a gradual decrease of activation to the native activity. This effect could not be related to the Mg-ATP = complexes since the enzymic preparation Mg(2+)-free still showed the same biphasic pattern of activation.     

Brain Insulin Dysregulation: Implication for Neurological and Neuropsychiatric Disorders

Arduous efforts have been made in the last three decades to elucidate the role of insulin in the brain. A growing number of evidences show that insulin is involved in several physiological function of the brain such as food intake and weight control, reproduction, learning and memory, neuromodulation and neuroprotection. In addition, it is now clear that insulin and insulin disturbances particularly diabetes mellitus may contribute or in some cases play the main role in development and progression of neurodegenerative and neuropsychiatric disorders. Focusing on the molecular mechanisms, this review summarizes the recent findings on the involvement of insulin dysfunction in neurological disorders like Alzheimer’s disease, Parkinson’s disease and Huntington’s disease and also mental disorders like depression and psychosis sharing features of neuroinflammation and neurodegeneration.     

Photosensitization effects on the solubility of acid phosphatase in nervous tissue

Summary Experiments of in vitro photosensitization of nervous tissue employing ultraviolet irradiation with oxygen and Acridinorange have been carried out. The histochemical and biochemical modifications of the acid phosphatase activities are discussed in line with an alteration of lysosomal membranes provoked by the photosensitizing process.Supported by Consiglio Nazionale delle Ricerche (CNR), Roma. Contr. N. 69.01686/115.3455.0.     

Serum haptoglobins in experimental coccidioidomycosis — A preliminary report

Summary The level of haptoglobin was determined in control rats and in rats infected withC. immitis. The haptoglobin levels in the infected group were significantly higher than in those in the control group. The possibility that serial determinations may be of value in following the course of this disease is currently being investigated.This study was supported in part by USPHS Grants A1-06048-01, 5 T1 A1 52–06 and the Dermatologic Research Foundation of California, Inc.