Histochemical Study of Photoperiodic and Low Temperature Effects on Floral Induction of Spinacia oleracea

Shoot apices of Spinacia oleracea plants have been induced toflower either by: (a) subjecting leaves to 24 h long day, or(b) exposure to a short photoperiod but displaced by 8 h (displacedshort day) in the usual 24 h short-day cycle, or (c) exposureto low temperature (5 °C) during the dark period of thenormal short day. A quantitative cytochemical assay of pentosephosphate pathway activity during floral induction indicatesan approximate doubling of the rate of activity when comparedto that of vegetative apices (short day) (21 °C). Exposure to either low temperature, or a displaced short photoperiodstimulates pentose phosphate pathway activity in the shoot apexin a manner similar to that seen by long-day induction. Thischange in metabolic activity is accompanied by changes in theshape of the shoot apex which resembles that seen at an earlystage during floral induction. Spinacia oleracea, pentose phosphate pathway, shoot apex, glucose-6-phosphate dehydrogenase, floral induction, chilling, displaced short day     

Histamine: correlative studies in nucleus accumbens

The role of histamine as a neurotransmitter has been the subject of considerable controversy. Recent evidence suggests it to be involved in such complex activities as arousal and affect. The purpose of the present study is to examine the possible source, function, and pharmacology of histamine in the nucleus accumbens, an area of the brain also implicated in complex activities such as affect. The anatomical studies suggest that the most probable source of the histamine in nucleus accumbens is the complex region lateral to the mammillary nuclei. These areas are the intercalated nucleus and the tuberomammillary nucleus (nuclei gemini hypothalami). To a lesser degree, the supramammillary complex may also contribute histamine-containing axons to the accumbens area. Adenylate cyclase in the rabbit nucleus accumbens displayed activation in response to histamine agonists (histamine, 2-Me-histamine, and 4-Me-histamine). The action of the H1 antagonist promethazine was greater than the H2 antagonist metiamide in reducing enzyme activation by histamine and 2-Me-histamine. In contrast, metiamide was more potent than promethazine toward antagonism of the action of 4-Me-histamine. However, no additive effects were noted when agonists were added in combination. Based upon these data, it is suggested that activation of adenylate cyclase in the rabbit nucleus accumbens is mediated in part by mixed H1 and H2 receptors or cellular disruption reflects the loss of receptor specificity. Physiological studies demonstrated that the H2 agonist 4-Me-histamine had an inhibitory effect on the activity of neurons driven by stimulation of the fimbria. The magnitude of the effect was frequency dependent. The H1 agonist 2-Me-histamine had no significant effect. Iontophoretic application of 4-Me-histamine had minimal effect upon low frequency volleys (0.5 Hz) but had a pronounced effect upon higher frequency volleys (6.0 Hz). These effects were antagonized by metiamide. Iontophoretic application of metiamide alone produced an effect only upon the P component of the field response, which is also bicuculline sensitive. Bicuculline coadministration was also effective in antagonizing the 4-Me-histamine effect. The physiological data suggest that histamine works through H2 receptors in nucleus accumbens, perhaps by potentiating the effects of gamma-aminobutyric acid (GABA). Thus, histamine in nucleus accumbens appears to function as a modulatory substance whose effect is dependent upon the activity of other transmitter and afferent systems.     

Phenolics Composition and Biological Activities Assessment of Leaves,Flowers and Roots Extracts from Erodium glaucophyllum,Erodium hirtum and Erodium guttatum

Biology Bulletin - Erodium glaucophyllum, Erodium hirtum and Erodium guttatum were medicinal herbs from a southern Mediterranean known for its health benefits. There is a strong demand for the find...     

Should I stay or should I go?: Shedding of RPTPs in cancer cells switches signals from stabilizing cell-cell adhesion to driving cell migration

Dissolution of cell-cell adhesive contacts and increased cell-extracellular matrix adhesion are hallmarks of the migratory and invasive phenotype of cancer cells. These changes are facilitated by growth factor binding to receptor protein tyrosine kinases (RTKs). In normal cells, cell-cell adhesion molecules (CAMs), including some receptor protein tyrosine phosphatases (RPTPs), antagonize RTK signaling by promoting adhesion over migration. In cancer, RTK signaling is constitutive due to mutated or amplified RTKs, which leads to growth factor independence or autonomy. An alternative route for a tumor cell to achieve autonomy is to inactivate cell-cell CAMs such as RPTPs. RPTPs directly mediate cell adhesion and regulate both cadherin-dependent adhesion and signaling. In addition, RPTPs antagonize RTK signaling by dephosphorylating molecules activated following ligand binding. Both RPTPs and cadherins are downregulated in tumor cells by cleavage at the cell surface. This results in shedding of the extracellular, adhesive segment and displacement of the intracellular segment, altering its subcellular localization and access to substrates or binding partners. In this commentary we discuss the signals that are altered following RPTP and cadherin cleavage to promote cell migration. Tumor cells both step on the gas (RTKs) and disconnect the brakes (RPTPs and cadherins) during their invasive and metastatic journey.Key words: receptor protein tyrosine kinase, receptor-like protein tyrosine phosphatase, cadherins, cell adhesion, signal transduction, phospholipase C gamma, protein kinase C, catenins, IQGAP1 protein, regulated intramembrane proteolysis     

Termites Improve the Horizontal Movement of Carbonized Particles: A Step towards Sustainable Utilization of Biochar

Soil amendments containing carbonized materials increase the soil carbon reservoir, influence plant productivity, and, ultimately, help to clean the environment. There is data on the effect of such additions on soil physicochemical properties or plant growth, but few studies have focused on how these carbonized materials are distributed by termite species in the soil ecosystem. It is the first comprehensive study of the transportation of biochar (BC) by termite species under tropical environmental conditions in Pakistan. The present study was carried out to test the hypothesis that if termite species I) were involved in the distribution of biochar particles II) if yes, then how far these particles were transported during the study period (10 days) and III) check their preference between the enriched BC (EBC) and non-enriched BC. BC was enriched with the cattle slurry after its pyrolysis in the study. The results showed that EBC particles were significantly more widely distributed than non-enriched BC particles, but both types of BC were transported more than 4 cm (ring 4) within 10 days (at the end of the experiment). The current study also revealed that EBC was easily attached to the setae, cuticle, and legs of termites, implying that it could potentially be transported over a greater distance. Furthermore, transportation of EBC over larger distances indicated a potential preference of termite species between the EBC and BC particles. During the study, however, the preference among the termite species was also observed. Under the prevailing study conditions, the Coptotermes heimi and Heteroterme indicola species transported the EBC further than Microtermes obesi and Odontotermes obesus. These findings revealed that transportation preferences were observed among the four termite species. In conclusion, the current study found that termites were involved in the distribution of BC particles, with a preference for EBC and that these have the potential to transport BC particles more than 4 cm within 10 days. Furthermore, two species Coptotermes heimi and Heteroterme indicola may be more suitable candidates for EBC transpiration in Pakistani soils. It was necessary to conduct additional research into the effect of temperature on the transportation process.     

The provision of supplementary fresh water improves the breeding success of the globally threatened Northern Bald Ibis Geronticus eremita

The Northern Bald Ibis Geronticus eremita is a globally threatened species with its main remaining world population breeding in an area of sea cliffs and coastal semi‐desert steppe near Agadir in southern Morocco. Between 1998 and 2002, we showed experimentally that the small‐scale provision of fresh water near the breeding colonies led to an increase in the productivity of the birds. The increase was greatest in years with low natural rainfall but was positive in all years tested. The supplementary fresh water appears to help buffer productivity against the impacts of low rainfall and its provision is now part of the ongoing conservation measures for this species.