Nitrogen fertigation of greenhouse-grown cucumber

Summary This greenhouse study investigated the response of trickle-irrigated cucumber (Cucumis sativa cv. ‘Petita’) to three N levels applied with every irrigation via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. Water containing 5.8, 11.8, or 17.8 mmol N/l, and uniformly supplied with 2.0 and 3.9 mmol/l of P and K, respectively, was applied two to three times daily. In all treatments of 0.3 leaching fraction was allowed. The resulting total N applications were 15.7, 31., and 47.2 g N/plant. The total amount of water applied was 1851/plant. Total N and NO₃-N, in lajinae and petioles, increased with increasing N level whereas P and K in generated decreased. Although different NO₃/NH₄ ratios in the treatments may have influeced the response to N, it could be concluded that the highest yield was obtained with 11.8 mmol N/1 due to increased number of fruit. In the root volume of this treatment the NO₃-N concentration in the soil solution was aroun 7 mmol/1 for most of the growing season. The dry matter concentration of fruits was not affected by the N levels. It was concluded that 11.8 mmol N/1 applied with every irrigation via the irrigation stream is adequate to cover the needs of greenhous-grown cucumber for higher yield (9.42 kg/plant over a harvesting period of 93 days).     

Selective Vulnerability of Spinal and Cortical Motor Neuron Subpopulations in delta7 SMA Mice

Loss of the survival motor neuron gene (SMN1) is responsible for spinal muscular atrophy (SMA), the most common inherited cause of infant mortality. Even though the SMA phenotype is traditionally considered as related to spinal motor neuron loss, it remains debated whether the specific targeting of motor neurons could represent the best therapeutic option for the disease. We here investigated, using stereological quantification methods, the spinal cord and cerebral motor cortex of ∆7 SMA mice during development, to verify extent and selectivity of motor neuron loss. We found progressive post-natal loss of spinal motor neurons, already at pre-symptomatic stages, and a higher vulnerability of motor neurons innervating proximal and axial muscles. Larger motor neurons decreased in the course of disease, either for selective loss or specific developmental impairment. We also found a selective reduction of layer V pyramidal neurons associated with layer V gliosis in the cerebral motor cortex. Our data indicate that in the ∆7 SMA model SMN loss is critical for the spinal cord, particularly for specific motor neuron pools. Neuronal loss, however, is not selective for lower motor neurons. These data further suggest that SMA pathogenesis is likely more complex than previously anticipated. The better knowledge of SMA models might be instrumental in shaping better therapeutic options for affected patients.     

Cytokine cross-talk between phagocytic cells and lymphocytes: Relevance for differentiation/activation of phagocytic cells and regulation of adaptive immunity

Cytokines represent one of the most important elements in the communication among different cell types. They play an increasingly better understood role in the communication among hematopoietic cells and in particular in the reciprocal regulation of effector cell types of innate or natural resistance (phagocytic cells and Natural Killer (NK) cells) and those of adaptive immunity (T and B lymphocytes). Lymphocytes produce several cytokines with either stimulatory (e.g., colony stimulatory factor) or suppressive (e.g., tumor necrosis factors and interferons) effects on proliferation of early hematopoietic cells. Many of these cytokines, alone or acting in synergistic combinations, also have a differentiation-inducing ability on immature myeloid cells and act as powerful potentiators of the cellular functions of terminally differentiated phagocytic cells. The communication between lymphocytes and phagocytic cells is not unidirectional, as phagocytic cells produce factors that regulate lymphocyte activation. In addition to their role as antigen presenting cells expressing costimulatory accessory molecules and secreting cytokines (e.g., IL-1, IL-6, TNF), phagocytic cells have been recently shown to produce Natural Killer cell Stimulatory Factor (NKSF/IL-12). IL-12 is a heterodimeric cytokine with important modulatory functions on cytotoxicity of NK and T cells, lymphocyte proliferation, lymphokine production, and development of T helper cell subsets. These communications between phagocytic cells and lymphocytes are further regulated by negative and positive feedback mechanisms that contribute to maintain the homeostasis of the system in physiologic conditions and to govern the changes in this equilibrium needed for the response to infectious or other foreign agents.     

Applications of artificial ionization

Summary The effects of positive and negative ions on man and on animals have been widely studied by numerous teams of researchers. It is well-known that negative ions have beeeficial effects on chronic and allergy-related bronchopathies in man; they stimulate the activity of the endocrine glands and psychomotor, muscular and cerebral functions. They have a beneficial effect on general circulation, and in particular on the microcirculatory system, such that they are suggested for use in prophylaxis and prevention of senescence, in acute, chronic and allergy-related pneumopathies, and in neuro-vegetative dystonia. The use of artificial negative ion producers may be a useful tool for both preventive and therapeutic purposes, as well as hygienic/domestic applications. Systematic measurements ere taken of negative ions artificially produced in a confined space. The spatial distribution of artificially-produced negative ions in a confined space is presented. Applications relative to artificial generators are also suggested in order to obtain repeatable experimental conditions.     

Dual compartment (bicameral) culture: role of basement membrane in epithelial differentiation

A number of years ago we reported that tight junctions between adjacent Sertoli cells subdivide the seminiferous epithelium into two compartments, basal and adluminal, thus forming the morphological basis of the blood-testis barrier. It is now generally believed that the special milieu created by the Sertoli cells in the adluminal compartment is essential for germ cell differentiation. In order to duplicate the compartmentalization that occurs in vivo, Sertoli cells were cultured in bicameral chambers on Millipore filters impregnated with a reconstituted basement membrane. Confluent monolayers of these cells were tall columnar (40–60 µ in height) and highly polarized. These Sertoli cell monolayers established electrical resistance that peaked when the Sertoli-Sertoli tight junctions developed in culture. In addition, the monolayers formed a permeability barrier to ³H-inulin and lanthanum nitrate. The bicameral chambers were utilized in a number of studies on protein secretion, and it was revealed that numerous proteens are secreted in a polarized manner. In another study, hormone- stimulated aromatase activity was measured in Sertoli cells grown on plastic culture dishes, plastic dishes coated with laminin or Matrigel, and in the bicameral chambers. Cell culture on basement membrane substrate decreased the FSH-dependent estrogen production. No estrogen production was observed when the Sertoli cells were cultured in the bicameral chambers. These results are in accord with the hypothesis that differentiated Sertoli cells lose their ability to metabolize androgen to estrogen in an hormone-dependent manner, whereas undifferentiated cells in culture, or in vivo, have a very active FSH-dependent aromatase activity. This bicameral culture system could serve as an important model system to examine various functions of Sertoli cells including interactions of Sertoli cells with germ, Leydig, and myoid cells.     

Intracellular distribution of DNA methyltransferase during the cell cycle

The intracellular distribution of DNA methyltransferase has been analyzed in synchronously proliferating human cells. The localization of DNA methyltransferase was determined immunocytochemically using monoclonal antibodies directed against this enzyme. DNA methyltransferase was found to accumulate predominantly in nuclei with weak cytoplasmic staining. The DNA methyltransferase antigen was absent in early G1 phase, appeared in late G1 prior to the onset of DNA synthesis and persisted throughout S and G2 phases of the cell cycle. Mitotic cells showed a particularly strong staining intensity. These results show that DNA methyltransferase levels fluctuate during the cell cycle. This has possible implications on the stability of the DNA methylation pattern.