Toxoplasma gondii-Induced Activation of EGFR Prevents Autophagy Protein-Mediated Killing of the Parasite

Toxoplasma gondii resides in an intracellular compartment (parasitophorous vacuole) that excludes transmembrane molecules required for endosome-lysosome recruitment. Thus, the parasite survives by avoiding lysosomal degradation. However, autophagy can re-route the parasitophorous vacuole to the lysosomes and cause parasite killing. This raises the possibility that T. gondii may deploy a strategy to prevent autophagic targeting to maintain the non-fusogenic nature of the vacuole. We report that T. gondii activated EGFR in endothelial cells, retinal pigment epithelial cells and microglia. Blockade of EGFR or its downstream molecule, Akt, caused targeting of the parasite by LC3(+) structures, vacuole-lysosomal fusion, lysosomal degradation and killing of the parasite that were dependent on the autophagy proteins Atg7 and Beclin 1. Disassembly of GPCR or inhibition of metalloproteinases did not prevent EGFR-Akt activation. T. gondii micronemal proteins (MICs) containing EGF domains (EGF-MICs; MIC3 and MIC6) appeared to promote EGFR activation. Parasites defective in EGF-MICs (MIC1 ko, deficient in MIC1 and secretion of MIC6; MIC3 ko, deficient in MIC3; and MIC1-3 ko, deficient in MIC1, MIC3 and secretion of MIC6) caused impaired EGFR-Akt activation and recombinant EGF-MICs (MIC3 and MIC6) caused EGFR-Akt activation. In cells treated with autophagy stimulators (CD154, rapamycin) EGFR signaling inhibited LC3 accumulation around the parasite. Moreover, increased LC3 accumulation and parasite killing were noted in CD154-activated cells infected with MIC1-3 ko parasites. Finally, recombinant MIC3 and MIC6 inhibited parasite killing triggered by CD154 particularly against MIC1-3 ko parasites. Thus, our findings identified EGFR activation as a strategy used by T. gondii to maintain the non-fusogenic nature of the parasitophorous vacuole and suggest that EGF-MICs have a novel role in affecting signaling in host cells to promote parasite survival

Night-time Changes in Field Strength of 11.8 MHz Radio Signals over Coldmbo-Ahmedabad Transmission Path

148-152The results of a study of night-time records of the field strength of radio signals on 11.8 MHz transmitted from Colombo (6.9ᵒN, 79.9ᵒE, I=5ᵒS) and obtained at Ahmedabad (23ᵒN, 72.6ᵒE, I=34ᵒN) are reported. It is shown that the maximum strength is observed an hour after sunset in summer and almost at sunset in winter. This maximum is most pronounced in equinoctial months. The records show a fast fading of small amplitude on quiet day’s characteristic of spread-F. On magnetically disturbed days, the field strength under-goes large fluctuations with reduced fading rate and absence of flutter-type fading. On some occasions of high magnetic activity, signals become very weak. Such changes are believed to be caused by large-scale movements in the F2-layer and the accompanying changes in the electron density during the magnetic storm. Several instances of temporary sharp increases of field strengths over duration of about 10 min have been recorded in the post-sunset to pre-midnight interval. Most of these are found to occur after solar radio bursts with a lag of 12-17 min. The observed effect of increased field strength may be due to a transient disturbance produced in the F2-layer due to the burst

Seasonal & Solar Control of Ionospheric Absorption at a Low Latitude Station

171-175Results of ionospheric absorption measured by Ai-method on internationally accepted standard frequency 2.2 MHz at Ahmedabad (23°N, 72.6°E; mag. dip 34°N) are presented for a period of over seven years (1972-1978)including solar minimum epoch in 1976.The diurnal index (n) of cos is found to be in anticorrelation with the time delay () in the diurnal maximum of absorption. The absorption at fixed values of cos shows better agreement with the sunspot number as well as S10.7 radio flux than its noontime (1200 hrs) value. Absorption at constant solar zenith angle () normalized to minimum solar activity shows two maxima in equinoxes corresponding to the atmospheric pressure maxima at 85-90 km. No significant correlation of n and is found with the index of solar activity. These are explained in terms of changes in the intensity of solar ultraviolet ionizing radiation and the atmospheric gas composition in the lower ionosphere with solar activity and the season

Differences Between AI-Absorption Values Measured with Sporadic-E & Normal-E Layer Reflections

1-4Ionospheric absorption measurements by Al method on 2'2 MHz over a period of 14 months at Ahmedabad indicated, in many cases, a distinction between the reflections from the normal-E layer and from totally reflecting low-type sporadic-E layer indicated by significantly lower virtual echo-heights. It appears that the absorption values obtained with these Es-reflections are generally low by about 35 per cent as compared to the total absorption-obtained with normal-E reflections. The above finding supports the view that the totally reflecting Es acts like a virtually loss-free reflector in contrast to the normal-E layer in which a considerable fraction of the total absorption occurs near the reflection level. A model calculation of absorption gives results consistent with the observed reduction in absorption

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Not AvailableFresh dried and old dried sangari (Prosopis cineraria) were treated with 0, 2.5, 5.0, and 7.0 kGy of irradiation and subsequently stored at ambient temperatures. Proximate values and total bacterial counts were evaluated immediately after irradiation and at regular intervals of 1 month during 3 months of storage. No significant changes were found in moisture, fat, protein, ash and fiber contents. Total sugar content was increased in both control and irradiated samples possibly due to conversion of starch into sugars. Irradiation treatment reduces total bacterial counts of dried samples of both fresh and old dried sangari. However, a dose of 5.0 kGy completely decontaminated both sangari and there was no microbial growth in 5.0 kGy irradiated samples during the storage period. Irradiation at 5.0 kGy was enough to extend the shelf-life of dried sangari up to 3 months without any significant change in the nutritional qualities.Not Availabl

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Not AvailableFresh dried and old (6–12 months) dried kachri (Cucumis callosus) were treated with 0, 2.5, 5 and 7 kGy of gamma radiation in a cobalt 60 gamma cell (GC-1200). The irradiated samples of kachri were stored at room temperature (28±2 °C). Total bacterial count and nutrient composition were evaluated immediately after irradiation and at regular intervals of 1 month during 3 months of storage. Results indicated that gamma radiation reduced the total bacterial counts of dried samples of both fresh and old dried kachri. Dose of 5.0 kGy was sufficient to eliminate total bacterial count and there was no microbial growth in 5.0 kGy irradiated samples during the storage period. No significant differences were observed in the proximate composition of both types of kachri at all irradiation doses. It was concluded that irradiation treatments of kachri improves keeping quality of both freshly dried and old dried Kachri.Not Availabl