Growth hormone modulation of EGF-induced PI3K-Akt pathway in mice liver

The epidermal growth factor (EGF) activates the phosphatidylinositol 3-kinase (PI3K)-Akt cascade among other signaling pathways. This route is involved in cell proliferation and survival, therefore, its dysregulation can promote cancer. Considering the relevance of the PI3K-Akt signaling in cell survival and in the pathogenesis of cancer, and that GH was reported to modulate EGFR expression and signaling, the objective of this study was to analyze the effects of increased GH levels on EGF-induced PI3K-Akt signaling.EGF-induced signaling was evaluated in the liver of GH-overexpressing transgenic mice and in their normal siblings. While Akt expression was increased in GH-overexpressing mice, EGF-induced phosphorylation of Akt, relative to its protein content, was diminished at Ser473 and inhibited at Thr308; consequently, mTOR, which is a substrate of Akt, was not activated by EGF. However, the activation of PDK1, a kinase involved in Akt phosphorylation at Thr308, was not reduced in transgenic mice. Kinetics studies of EGF-induced Akt phosphorylation showed that it is rapidly and transiently induced in GH-overexpressing mice compared with normal siblings. Thus, the expression and activity of phosphatases involved in the termination of the PI3K-Akt signaling were studied. In transgenic mice, neither PTEN nor PP2A were hyperactivated; however, EGF induced the rapid and transient association of SHP-2 to Gab1, which mediates association to EGFR and activation of PI3K. Rapid recruitment of SHP2, which would accelerate the termination of the proliferative signal induced, could be therefore contributing to the diminished EGF-induced activity of Akt in GH-overexpressing mice.     

Response to Arsenate Treatment in Schizosaccharomyces pombe and the Role of Its Arsenate Reductase Activity

Arsenic toxicity has been studied for a long time due to its effects in humans. Although epidemiological studies have demonstrated multiple effects in human physiology, there are many open questions about the cellular targets and the mechanisms of response to arsenic. Using the fission yeast Schizosaccharomyces pombe as model system, we have been able to demonstrate a strong activation of the MAPK Spc1/Sty1 in response to arsenate. This activation is dependent on Wis1 activation and Pyp2 phosphatase inactivation. Using arsenic speciation analysis we have also demonstrated the previously unknown capacity of S. pombe cells to reduce As (V) to As (III). Genetic analysis of several fission yeast mutants point towards the cell cycle phosphatase Cdc25 as a possible candidate to carry out this arsenate reductase activity. We propose that arsenate reduction and intracellular accumulation of arsenite are the key mechanisms of arsenate tolerance in fission yeast.     

Further experience in stereotactic pontine tractotomy

The problem with percutaneous and even stereotactic cordotomy is the difficulty in obtaining sufficiently high analgesic levels without autonomic complications, although the problem seemed to apply to relatively few patients since percutaneous and stereotactic spinal procedures achieved sufficiently high analgesic levels to encompass most patients' pain. There is a group of patients, however, with high pain in the shoulder and neck where conventional percutaneous and stereotactic spinal procedure are dangerous. From the standpoint of achieving high levels of analgesia with a low incidence of dysaesthesia, pontomedullary lesions appear to have advantages.     

Biological Data on <Emphasis Type="Italic">Anovia punica</Emphasis> Gordon (Coleoptera: Coccinellidae), a Predator of <Emphasis Type="Italic">Crypticerya multicicatrices</Emphasis> Kondo &amp; Unruh (Hemiptera: Monophlebidae)

The coccinellid beetle Anovia punica Gordon (Coleoptera: Coccinellidae: Noviini) is an important predator of the Colombian fluted scale, Crypticerya multicicatrices Kondo & Unruh (Hemiptera: Monophlebidae). In order to gather information on the biological traits of A. punica, we conducted a series of studies, including of the developmental time of each life history stage, estimation of life table parameters, and predation rates under laboratory conditions [25.1 ± 1.6°C, with 70.5 ± 7.3% RH, and natural light regime, approx. 12:12 (L:D) h]. Developmental stages of A. punica were categorized as follows: egg stage, four larval instars, prepupal instar, pupal instar, and adult. Developmental time from egg to adult emergence averaged 29.41 ± 1.85 days, and 47.6% of the eggs developed to adulthood. Female and male survival was 94.42 and 90 days, respectively. Life table parameters show that one female of A. punica is replaced by 86 females (R ₀), the intrinsic growth rate (r _m ) was 0.1115, the average generation time (T) was 40 days, and the doubling time (D _t ) was 6.2 days. The life table parameters suggest that A. punica can be used as a potential predator of C. multicicatrices and, more importantly, provided baseline information for a mass-rearing protocol. This is the first detailed study on the biology of A. punica that reports the potential of this predator as a biological control agent for scale insects of the tribe Iceryini.     

SPECIALIZED MEMBRANE JUNCTIONS BETWEEN NEURONS IN THE VERTEBRATE CEREBELLAR CORTEX

"Gap" junctions, the morphological correlate for low-resistance junctions, are demonstrated between some mossy fiber terminals and granule cell dendrites in some lower vertebrate cerebella (gymnotid and frog). Most of the gap junctions (GJs) seen in the gymnotid-fish cerebellum exhibit an asymmetrical configuration, the electron-opaque cytoplasmic material underlying the junction being more extensive in the dendritic than in the axonal side. In the frog cerebellum, the GJs have a symmetrical distribution of such electron-opaque material. In both species the GJs are encountered at the same synaptic interface as the conventional synaptic zone (CSZ), constituting "mixed synapses" in a morphological sense. The axonal surface covered by CSZs is larger than that covered by GJs. In mammalian cerebellum, GJs are observed only in the molecular layer, between perikarya, dendrites, or perikarya and dendrites of the inhibitory interneurons. These GJs are intermixed with attachment plates and intermediary junctions interpreted as simply adhesive. In the mammalian cerebellum, a new type of junction which resembles the septate junctions (SJs) of invertebrate epithelia is observed between axonal branches forming the tip of the brush of basket fibers around the initial segment of the Purkinje cell axon. It is suggested that such junctions may be modified forms of septate junctions. The physiological implications of the possible existence of high-resistance cross-bridges between basket cell terminals, which may compartmentalize the extracellular space and thus regulate extracellular current flow, must be considered.     

On the Biology of the Colombian Fluted Scale, <Emphasis Type="Italic">Crypticerya multicicatrices</Emphasis> Kondo &amp; Unruh (Hemiptera: Monophlebidae)

The Colombian fluted scale Crypticerya multicicatrices Kondo & Unruh (Hemiptera: Monophlebidae) is a polyphagous insect pest native to continental Colombia and reported on 148 species, mainly palms (Arecaceae); mango, Mangifera indica (Anacardiaceae); and leguminous trees and shrubs (Fabaceae). The biology and ecological parameters of C. multicicatrices were investigated using as a host plant Caesalpinia pluviosa var. peltophoroides (Fabaceae) under two environmental conditions: semifield (max temp., 31.5?±?3.0°C; max. RH, 78.9?±?6.0%) and a glass house (max. temp., 37.1?±?5.1°C, max. RH, 67.0?±?6.2%) in the premises of Corpoica, Palmira Research Station. The duration of the different developmental stages was highly different under both temperature conditions. First- and third-instar nymphs, the period of ovisac growth of the adult, and the duration of the life cycle were significantly higher in the semifield conditions compared to the glass house conditions. In contrast, the second-instar nymph stage was shorter in the semifield conditions. The duration of the fourth-instar stage (adult) and the reproductive period were the same in both environments. As for the evaluated ecological parameters, a great difference was found between the two environmental conditions, where the net reproductive rate (R _o) and mean generation time (T) were significantly higher in the semifield conditions than in the glass house conditions. The obtained biological and ecological information is an essential tool for finding strategies to control this insect pest. This is the first detailed study on the biology of a species in the genus Crypticerya Cockerell.     

Taenia crassiceps cysticercosis in mice does not increase the carcinogenic effect of methyl-nitrosourea

An association between brain cysticercosis and malignant neoplasms in humans has recently been reported. To explore the possibility of a potentiating effect of cysticercosis on carcinogenesis mice infected with Taenia crassiceps cysticerci were exposed to the carcinogenic substance methyl-nitrosourea; 35% of them developed lymphoma, in contrast with 50% of control non-infected animals exposed to MNU. In this experimental model of cysticercosis we did not find a potentiating effect of peritoneal cysticercosis on the carcinogenicity of MNU.