Muscle damage induced by the ionophore A23187 can be prevented by prostaglandin inhibitors and leupeptin

Summary Frog skeletal muscle incubated in vitro with the ionophore A23187 shows extensive morphological alterations. Myofilament disruption, presumably mediated by excess intracellular calcium, can be partially prevented by preincubating the muscle with inhibitors of prostaglandin synthesis and the lysosomal thiol protease inhibitor leupeptin.The author would like to thank Dr R. J. Walter for helpful comments and Ms V. Kriho for valuable technical assistance     

Muscle damage induced by the ionophore A23187 can be prevented by prostaglandin inhibitors and leupeptin

Frog skeletal muscle incubated in vitro with the ionophore A23187 shows extensive morphological alterations. Myofilament disruption, presumably mediated by excess intracellular calcium, can be partially prevented by preincubating the muscle with inhibitors of prostaglandin synthesis and the lysosomal thiol protease inhibitor leupeptin.     

Nicotinamide is an inhibitor of SIRT1 in vitro,but can be a stimulator in cells

Nicotinamide (NAM), a form of vitamin B₃, plays essential roles in cell physiology through facilitating NAD⁺ redox homeostasis and providing NAD⁺ as a substrate to a class of enzymes that catalyze non-redox reactions. These non-redox enzymes include the sirtuin family proteins which deacetylate target proteins while cleaving NAD⁺ to yield NAM. Since the finding that NAM exerts feedback inhibition to the sirtuin reactions, NAM has been widely used as an inhibitor in the studies where SIRT1, a key member of sirtuins, may have a role in certain cell physiology. However, once administered to cells, NAM is rapidly converted to NAD⁺ and, therefore, the cellular concentration of NAM decreases rapidly while that of NAD⁺ increases. The result would be an inhibition of SIRT1 for a limited duration, followed by an increase in the activity. This possibility raises a concern on the validity of the interpretation of the results in the studies that use NAM as a SIRT1 inhibitor. To understand better the effects of cellular administration of NAM, we reviewed published literature in which treatment with NAM was used to inhibit SIRT1 and found that the expected inhibitory effect of NAM was either unreliable or muted in many cases. In addition, studies demonstrated NAM administration stimulates SIRT1 activity and improves the functions of cells and organs. To determine if NAM administration can generate conditions in cells and tissues that are stimulatory to SIRT1, the changes in the cellular levels of NAM and NAD⁺ reported in the literature were examined and the factors that are involved in the availability of NAD⁺ to SIRT1 were evaluated. We conclude that NAM treatment can hypothetically be stimulatory to SIRT1.     

Neural discharge can be modulated by carotid arterial injection of gastrin-17 in rat hypothalamic paraventricular nucleus

Neural discharge in the hypothalamic paraventricular nucleus (PVN) was examined after gastrin-17 injection into the carotid artery in anesthetized rats. Neural discharge was increased by gastrin-17 injection into the carotid artery close to the cranium, and the response due to the gastrin was dose-dependent. No discharge response was seen when gastrin was injected into the jugular vein. These results suggest that gastrin circulating in the arterial blood can penetrate the blood brain barrier, and modulate neural PVN activity which is responsible for gastric acid secretion.     

Seasonal variations in mitosis in the frog: a field study.

Field studies have shown that there is a seasonal variation in mitosis of lens and corneal epithelium (high in May and June, low during the rest of the year). This phenomenon can be reproduced in the laboratory by temperature manipulation. The response in the lens depends on the presence of the pituitary gland while the corneal one seems to be independent of it.     

Immobile survival of motoneuron (SMN) protein stored in Cajal bodies can be mobilized by protein interactions

Reduced levels of survival of motoneuron (SMN) protein lead to spinal muscular atrophy, but it is still unknown how SMN protects motoneurons in the spinal cord against degeneration. In the nucleus, SMN is associated with two types of nuclear bodies denoted as gems and Cajal bodies (CBs). The 23 kDa isoform of fibroblast growth factor-2 (FGF-2²³) is a nuclear protein that binds to SMN and destabilizes the SMN-Gemin2 complex. In the present study, we show that FGF-2²³ depletes SMN from CBs without affecting their general structure. FRAP analysis of SMN-EGFP in CBs demonstrated that the majority of SMN in CBs remained mobile and allowed quantification of fast, slow and immobile nuclear SMN populations. The potential for SMN release was confirmed by in vivo photoconversion of SMN-Dendra2, indicating that CBs concentrate immobile SMN that could have a specialized function in CBs. FGF-2²³ accelerated SMN release from CBs, accompanied by a conversion of immobile SMN into a mobile population. Furthermore, FGF-2²³ caused snRNP accumulation in CBs. We propose a model in which Cajal bodies store immobile SMN that can be mobilized by its nuclear interaction partner FGF-2²³, leading to U4 snRNP accumulation in CBs, indicating a role for immobile SMN in tri-snRNP assembly.     

Gamma globulins in the mice vaginal fluids: Cyclic and experimental variations

Summary The study of the gamma globulins in the vaginal fluids reveals that the lowest values were found in mice at estrus and in castrated mice 8 days after the estrogen treatment. We suggest that the variation of gamma globulins in the vaginal fluids is influenced both under physiological and experimental conditions by estrogens.This work was supported by a grant of the Conicet No. 4973 b/74.Fellow of Scientific Investigator Career. Consejo Nacional de Investigaciones Cientificas y Técnicas.Member of Scientific Investigator Career. Consejo Nacional de Investigaciones Científicas y Técnicas.     

Gamma globulins in the mice vaginal fluids: cyclic and experimental variations.

The study of the gamma globulins in the vaginal fluids reveals that the lowest values were found in mice at estrus and in castrated mice 8 days after the estrogen treatment. We suggest that the variation of gamma globulins in the vaginal fluids is influenced both under physiological and experimental conditions by estrogens.     

Esterases in avian sera: Species specific pattern and individual variations

Résumé Les taches colorées correspondant à l'activité estérasique des sérums d'oiseaux, après électrophorèse en gélose, diffèrent entre elles en nombre, localization et relative intensité de coloration dans les sérums provenant de familles différentes: Poules, Canards, Pigeons ou d'espèces d'une même famille. Chez certaines espèces, on peut également observer des variations individuelles.     

Cytokinesis in development and disease: variations on a common theme

Cytokinesis is a crucial step in cell proliferation, and remarkably, it is also an important mechanism for developmental regulation in the generation of diverse cell types in eukaryotic organisms. Successful cytokinesis relies on the assembly and activation of an actomyosin-based contractile ring and membrane deposition/fusion in a spatially and temporally precise manner. As such, the molecular pathways governing cytokinesis are highly complex, involving a large number of components forming intricate interactive networks. The complexity of this system, however, may have also provided a rich platform for evolutionary ‘tinkering’ to achieve specific morphogenetic and developmental outcomes. Furthermore, failed or altered cytokinesis appears to contribute to the development of cancer in unexpected ways. Received 25 June 2007; received after revision 20 July 2007; accepted 16 August 2007     

Agroforestry in Mexico: Can the past be a guarantee for the future?

Some aspects of agroforestry systems in Mexico are reviewed, including the chinampas, a unique type of prehispanic home-garden, still in use today, mainly in the Mexico valley; the Huastec té'lom (in the north of Veracruz State) an agroforestry technique used by the farmers for sustainable exploitation of natural resources; and forest-farming among the Maya (Yucatan), a production strategy which has evolved over a long period. Some other, more recent agroforesting techniques are also reviewed. The discussion emphasizes the biological, ecological and social significance of agroforestry systems. Agroforestry, however, must be considered within its socio-economic context. Assessing the needs and potentialities of a region must be the first step towards integrating agroforestry systems into the socio-economic realities of today.     

Seasonal plasma testosterone variations in the stone marten]

Plasma testosterone levels change with annual sexual cycle of the stone marten. Very low during the decrease and the quiescence of the testis, it rises during the testis onset and reaches a maximal peak during the co?t period (May to July).     

Different roles of the human Orc6 protein in the replication initiation process

In eukaryotes, binding of the six-subunit origin recognition complex (ORC) to DNA provides an interactive platform for the sequential assembly of pre-replicative complexes. This process licenses replication origins competent for the subsequent initiation step. Here, we analyze the contribution of human Orc6, the smallest subunit of ORC, to DNA binding and pre-replicative complex formation. We show that Orc6 not only interacts with Orc1–Orc5 but also with the initiation factor Cdc6. Biochemical and imaging experiments reveal that this interaction is required for licensing DNA replication competent. Furthermore, we demonstrate that Orc6 contributes to the interaction of ORC with the chaperone protein HMGA1a (high mobility group protein A1a). Binding of human ORC to replication origins is not specified at the level of DNA sequence and the functional organization of origins is poorly understood. We have identified HMGA1a as one factor that might direct ORC to AT-rich heterochromatic regions. The systematic analysis of the interaction between ORC and HMGA1a revealed that Orc6 interacts with the acidic C-terminus of HMGA1a and also with its AT-hooks. Both domains support autonomous replication if targeted to DNA templates. As such, Orc6 functions at different stages of the replication initiation process. Orc6 can interact with ORC chaperone proteins such as HMGA1a to facilitate chromatin binding of ORC and is also an essential factor for pre-RC formation.