Effect of EGF-Receptor Tyrosine Kinase Inhibitor on Rab5 Function During Endocytosis

Tyrosine autophosphorylation within the cytoplasmic tail of EGF-receptor is a key event, which in turn recruits several factors including Shc, Grb2 and Rin1 that are essential activities for receptor-mediated endocytosis and signaling. In this study, we demonstrated that treatment with AG1478, an EGF-receptor kinase inhibitor, blocked the formation of Rab5-positive endosomes as well as the activation of Rab5 upon addition of EGF. We also found that EGF-receptor catalytically inactive mutant failed to activate Rab5 upon EGF stimulation. Additionally, endosomal co-localization of Rab5 and EGF-receptor was inhibited by AG1478. Interestingly, AG1478 inhibitor did not block the formation of enlarged Rab5-positive endosomes in cells expressing Rab5 GTP hydrolysis defective mutant (Rab5:Q79L). AG1478 inhibitor also blocked the in vitroendosome fusion in a concentration-dependent manner, and more importantly, Rab5:Q79L mutant rescued it. Furthermore, addition of Rin1, a Rab5 guanine nucleotide exchange factor, partially restored endosome fusion in the presence of AG1478 inhibitor. Consistent with these observations, we also observed that Rin1 was unable to localize to membranes upon EGF-stimulation in the presence of AG1478 inhibitor. These results constitute first evidence that the enzymatic activity of a tyrosine kinase receptor is required endosome fusion via the activation of Rab5

Sequential actions of Rab5 and Rab7 regulate endocytosis in the Xenopus oocyte

To explore the role of GTPases in endocytosis, we developed an assay using Xenopus oocytes injected with recombinant proteins to follow the uptake of the fluid phase marker HRP. HRP uptake was inhibited in cells injected with GTPγ S or incubated with aluminum fluoride, suggesting a general role for GTPases in endocytosis. Injection of Rab5 into oocytes, as well as Rab5:Q79L, a mutant with decreased GTPase activity, increased HRP uptake. Injection of Rab5:S34N, the dominant-negative mutant, inhibited HRP uptake. Injection of N-ethylmaleimide-sensitive factor (NSF) stimulated HRP uptake, and ATPase-defective NSF mutants inhibited HRP uptake when coinjected with Rab5:Q79L, confirming a requirement for NSF in endocytosis. Surprisingly, injection of Rab7:WT stimulated both uptake and degradation/activation of HRP. The latter appears to be due to enhanced transport to a late endosomal/prelysosomal degradative compartment that is monensin sensitive. Enhancement of uptake by Rab7 appears to function via an Rab5-sensitive pathway in oocytes since the stimulatory effect of Rab7 was blocked by coinjection of Rab5:S34N. Stimulation of uptake by Rab5 was blocked by Rab5:S34N but not by Rab7:T22N. Our results suggest that Rab7, while functioning downstream of Rab5, may be rate limiting for endocytosis in oocytes

Regulation of Rab5 Function during Phagocytosis of Live Pseudomonas aeruginosa in Macrophages

Pseudomonas aeruginosa, a Gram-negative opportunistic human pathogen, is a frequent cause of severe hospital-acquired infections. Effectors produced by the type III secretion system disrupt mammalian cell membrane trafficking and signaling and are integral to the establishment of P. aeruginosa infection. One of these effectors, ExoS, ADP-ribosylates several host cell proteins, including Ras and Rab GTPases. In this study, we demonstrated that Rab5 plays a critical role during early stages of P. aeruginosa invasion of J774-Eclone macrophages. We showed that live, but not heat-inactivated, P. aeruginosa inhibited phagocytosis and that this occurred in conjunction with downregulation of Rab5 activity. Inactivation of Rab5 was dependent on ExoS ADP-ribosyltransferase activity, and in J744-Eclone cells, ExoS ADP-ribosyltransferase activity caused a more severe inhibition of phagocytosis than ExoS Rho GTPase activity. Furthermore, we found that expression of Rin1, a Rab5 guanine exchange factor, but not Rabex5 and Rap6, partially reversed the inactivation of Rab5 during invasion of live P. aeruginosa. These studies provide evidence that live P. aeruginosa cells are able to influence their rate of phagocytosis in macrophages by directly regulating activation of Rab5

Bound on the neutrino magnetic moment from chirality flip in supernovae

For neutrinos with a magnetic moment, we show that the collisions in a hot and dense plasma act as an efficient mechanism for the conversion of $\nu_L$ into $\nu_R$. The production rate for right-handed neutrinos is computed in terms of a resummed photon propagator which consistently incorporates the background effects. Assuming that the entire energy in a supernova collapse is not carried away by the $\nu_R$, our results can be used to place an upper limit on the neutrino magnetic moment $\mu_\nu < (0.1-0.4)\times 10^{-11}\mu_B$Comment: 11 pages, minor changes, new title. Final version to appear in Phys. Rev. D (rapid communication

Intestinal parasitosis in relation to socioeconomic factors and habitat conditions in children of Neuquén, Patagonia, Argentina

The prevalence and distribution of intestinal parasites (IP) were investigated in children from two populations of different socioeconomic level, located in the same area of the city of Neuquén, in order to evaluate their relationship with habitat conditions and socioeconomic factors. Serial samples of faeces and anal scraping of 126 children between 2 and 14 years from two sectors of the suburban area of Neuquen (Sector I and Sector II) were analyzed. Data concerning habitat conditions and socioeconomic parameters were obtained by home visits and an observational structured survey. Presence of IP was detected in 50.7% of children from Sector I (suburban neighborhood with adequate sanitary conditions and middle or middle low socioeconomic level) and in 92.9% from children of Sector II (marginal settlement with poor sanitary conditions and low socioeconomic status). Seven intestinal protozoan and 4 helminth species were identified. Blastocystis hominis was the most frequent species found in both populations. No helminths different from Enterobius vermicularis were found in Sector I and the prevalence of such species was very low in Sector II. Deficient habitat conditions and low socioeconomic parameters showed relation with a higher prevalence of IP of direct transmission as protozoan and E.vermicularis in the studied populations. Nevertheless, even in this context favourable to transmission, the parasitic species which require intermediate stages of development in soil, don’t find an adequate habitat for dissemination in this region.Se investigó la prevalencia y distribución de parásitos intestinales (PI) en niños de 2 poblaciones de diferente nivel socioeconómico del área periurbana de la ciudad de Neuquén (Sectores I y II) a fin de evaluar su relación con las condiciones de hábitat y factores socioeconómicos. Se procesaron muestras seriadas de materia fecal y de escobillado anal de 126 niños entre 2 y 14 años de edad. Se registraron datos acerca de condiciones de hábitat y factores socioeconómicos mediante visitas domiciliarias y encuestas observaciones estructuradas. Se detectó presencia de PI en el 50,7% de los niños del Sector I (barrio suburbano con adecuadas condiciones sanitarias y nivel socioeconómico medio o medio-bajo) y en el 92,9% de los niños del Sector II (asentamiento marginal con deficientes condiciones sanitarias y bajo nivel socioeconómico). Se identificaron 7 especies de protozoos intestinales y 4 especies de helmintos. Blastocystis hominis fue la especie más frecuente encontrada en ambas poblaciones. No se encontraron helmintos diferentes de Enterobius vermicularis en el Sector I y la prevalencia de tales especies fue muy baja en el Sector II. Las condiciones de hábitat deficientes y los bajos parámetros socioeconómicos se relacionaron con una mayor prevalencia de PI de transmisión directa como protozoos y E. vermicularis en las poblaciones estudiadas. Sin embargo, aún en ese contexto favorable a la transmisión, las especies parasitarias que requieren estadíos intermedios de maduración en el suelo no encuentran un hábitat adecuado para su diseminación en esta región patagónica.Facultad de Ciencias Médica

Intestinal parasitosis in relation to socioeconomic factors and habitat conditions in children of Neuquén, Patagonia, Argentina

The prevalence and distribution of intestinal parasites (IP) were investigated in children from two populations of different socioeconomic level, located in the same area of the city of Neuquén, in order to evaluate their relationship with habitat conditions and socioeconomic factors. Serial samples of faeces and anal scraping of 126 children between 2 and 14 years from two sectors of the suburban area of Neuquen (Sector I and Sector II) were analyzed. Data concerning habitat conditions and socioeconomic parameters were obtained by home visits and an observational structured survey. Presence of IP was detected in 50.7% of children from Sector I (suburban neighborhood with adequate sanitary conditions and middle or middle low socioeconomic level) and in 92.9% from children of Sector II (marginal settlement with poor sanitary conditions and low socioeconomic status). Seven intestinal protozoan and 4 helminth species were identified. Blastocystis hominis was the most frequent species found in both populations. No helminths different from Enterobius vermicularis were found in Sector I and the prevalence of such species was very low in Sector II. Deficient habitat conditions and low socioeconomic parameters showed relation with a higher prevalence of IP of direct transmission as protozoan and E.vermicularis in the studied populations. Nevertheless, even in this context favourable to transmission, the parasitic species which require intermediate stages of development in soil, don’t find an adequate habitat for dissemination in this region.Se investigó la prevalencia y distribución de parásitos intestinales (PI) en niños de 2 poblaciones de diferente nivel socioeconómico del área periurbana de la ciudad de Neuquén (Sectores I y II) a fin de evaluar su relación con las condiciones de hábitat y factores socioeconómicos. Se procesaron muestras seriadas de materia fecal y de escobillado anal de 126 niños entre 2 y 14 años de edad. Se registraron datos acerca de condiciones de hábitat y factores socioeconómicos mediante visitas domiciliarias y encuestas observaciones estructuradas. Se detectó presencia de PI en el 50,7% de los niños del Sector I (barrio suburbano con adecuadas condiciones sanitarias y nivel socioeconómico medio o medio-bajo) y en el 92,9% de los niños del Sector II (asentamiento marginal con deficientes condiciones sanitarias y bajo nivel socioeconómico). Se identificaron 7 especies de protozoos intestinales y 4 especies de helmintos. Blastocystis hominis fue la especie más frecuente encontrada en ambas poblaciones. No se encontraron helmintos diferentes de Enterobius vermicularis en el Sector I y la prevalencia de tales especies fue muy baja en el Sector II. Las condiciones de hábitat deficientes y los bajos parámetros socioeconómicos se relacionaron con una mayor prevalencia de PI de transmisión directa como protozoos y E. vermicularis en las poblaciones estudiadas. Sin embargo, aún en ese contexto favorable a la transmisión, las especies parasitarias que requieren estadíos intermedios de maduración en el suelo no encuentran un hábitat adecuado para su diseminación en esta región patagónica.Facultad de Ciencias Médica

Movement Behavior of High-Heeled Walking: How Does the Nervous System Control the Ankle Joint during an Unstable Walking Condition?

The human locomotor system is flexible and enables humans to move without falling even under less than optimal conditions. Walking with high-heeled shoes constitutes an unstable condition and here we ask how the nervous system controls the ankle joint in this situation? We investigated the movement behavior of high-heeled and barefooted walking in eleven female subjects. The movement variability was quantified by calculation of approximate entropy (ApEn) in the ankle joint angle and the standard deviation (SD) of the stride time intervals. Electromyography (EMG) of the soleus (SO) and tibialis anterior (TA) muscles and the soleus Hoffmann (H-) reflex were measured at 4.0 km/h on a motor driven treadmill to reveal the underlying motor strategies in each walking condition. The ApEn of the ankle joint angle was significantly higher (p<0.01) during high-heeled (0.38±0.08) than during barefooted walking (0.28±0.07). During high-heeled walking, coactivation between the SO and TA muscles increased towards heel strike and the H-reflex was significantly increased in terminal swing by 40% (p<0.01). These observations show that high-heeled walking is characterized by a more complex and less predictable pattern than barefooted walking. Increased coactivation about the ankle joint together with increased excitability of the SO H-reflex in terminal swing phase indicates that the motor strategy was changed during high-heeled walking. Although, the participants were young, healthy and accustomed to high-heeled walking the results demonstrate that that walking on high-heels needs to be controlled differently from barefooted walking. We suggest that the higher variability reflects an adjusted neural strategy of the nervous system to control the ankle joint during high-heeled walking

Chaotic Signatures of Heart Rate Variability and Its Power Spectrum in Health, Aging and Heart Failure

A paradox regarding the classic power spectral analysis of heart rate variability (HRV) is whether the characteristic high- (HF) and low-frequency (LF) spectral peaks represent stochastic or chaotic phenomena. Resolution of this fundamental issue is key to unraveling the mechanisms of HRV, which is critical to its proper use as a noninvasive marker for cardiac mortality risk assessment and stratification in congestive heart failure (CHF) and other cardiac dysfunctions. However, conventional techniques of nonlinear time series analysis generally lack sufficient sensitivity, specificity and robustness to discriminate chaos from random noise, much less quantify the chaos level. Here, we apply a ‘litmus test’ for heartbeat chaos based on a novel noise titration assay which affords a robust, specific, time-resolved and quantitative measure of the relative chaos level. Noise titration of running short-segment Holter tachograms from healthy subjects revealed circadian-dependent (or sleep/wake-dependent) heartbeat chaos that was linked to the HF component (respiratory sinus arrhythmia). The relative ‘HF chaos’ levels were similar in young and elderly subjects despite proportional age-related decreases in HF and LF power. In contrast, the near-regular heartbeat in CHF patients was primarily nonchaotic except punctuated by undetected ectopic beats and other abnormal beats, causing transient chaos. Such profound circadian-, age- and CHF-dependent changes in the chaotic and spectral characteristics of HRV were accompanied by little changes in approximate entropy, a measure of signal irregularity. The salient chaotic signatures of HRV in these subject groups reveal distinct autonomic, cardiac, respiratory and circadian/sleep-wake mechanisms that distinguish health and aging from CHF