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1.
Background impulse activity (BIA) of neuronal elements of the fastigial nucleus (FN) of rat cerebellum were investigated for the first time with the aid of various methods of statistical analysis. A clear predominance of stationary impulse flows (IFs) was discovered, along with irregularities in such flows, variously expressed and including a significant number of realizations of a regular component of impulse activity. Nonstationary IFs constituted a special variety of BIA; they were found in 15% of the total number of neurons investigated. Serial correlation analysis of the durations of interspike intervals (ISIs), both of stationary and nonstationary IFs, allowed us to identify six main varieties of ISI dynamics in the BIA of neurons of the fastigial nucleus. The patterns of recorded IFs and variations in IFs can serve as an adequate indices of the state of cellular activity during intracellular recording from cells of the central nervous system.L. A. Orbeli Institute of Physiology, Armenian Academy of Sciences, Yerevan. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 441–450, July–August, 1991. 相似文献
2.
It is shown that inclusion of gangliosides into planar phospholipid bilayers leads to an essential suppression of their monolayer fusion. In contrast to phospholipid lysoforms, the gangliosides do not cause an associative decrease of the specific energy of the hydrophilic pore edge determined in the experiments on the electrical breakdown of membranes. This phenomenon depends on the effective size of the polar headgroup of the gangliosides. It is supposed that the effect of gangliosides on the parameters mentioned is based on the fact that they have large hydrated polar headgroups which create steric hindrances, which prevent (i) the membranes to come into contact during monolayer fusion; (ii) the gangliosides to take part in hydrophilic pore formation. 相似文献
3.
Stephen GS Vreden Jeetendra K Jitan Rakesh D Bansie Malti R Adhin 《Memórias do Instituto Oswaldo Cruz》2013,108(8):968-973
The emerging resistance to artemisinin derivatives that has been reported in
South-East Asia led us to assess the efficacy of artemether-lumefantrine as the first
line therapy for uncomplicated Plasmodium falciparum infections in
Suriname. This drug assessment was performed according to the recommendations of the
World Health Organization in 2011. The decreasing number of malaria cases in
Suriname, which are currently limited to migrating populations and gold miners,
precludes any conclusions on artemether efficacy because adequate numbers of patients
with 28-day follow-up data are difficult to obtain. Therefore, a comparison of day 3
parasitaemia in a 2011 study and in a 2005/2006 study was used to detect the
emergence of resistance to artemether. The prevalence of day 3 parasitaemia was
assessed in a study in 2011 and was compared to that in a study in 2005/2006. The
same protocol was used in both studies and artemether-lumefantrine was the study
drug. Of 48 evaluable patients in 2011, 15 (31%) still had parasitaemia on day 3
compared to one (2%) out of 45 evaluable patients in 2005/2006. Overall, 11 evaluable
patients in the 2011 study who were followed up until day 28 had negative slides and
similar findings were obtained in all 38 evaluable patients in the 2005/2006 study.
The significantly increased incidence of parasite persistence on day 3 may be an
indication of emerging resistance to artemether. 相似文献
4.
Decreased fertility was observed in a breeding colony of C57BL/6J mice. On examination, a dorsoventral vaginal septum was detected in many females. This defect was identified in 1976, with incidence of 4.0% in this strain. Our objective was to determine whether incidence of this condition has increased and whether this defect was associated with the observed infertility. We report incidence of 11.3%, nearly triple the original reported incidence. For comparison, incidence of vaginal septum in C57BL/6N females was determined and was found to be 1%. We performed a breeding study using normal and affected C57BL/6J females to evaluate fertility in affected females. Our data were consistent with those of the 1976 report; fertility was decreased in females with an intact vaginal septum. In 50% of affected females, the septum remained intact after breeding. The fertility for this subgroup of vaginal septum-retained females was 14.3%, compared with 85.7% in females whose septum ruptured and 75.0% in normal females (statistically significant, P = 0.02). On the basis of our results, we provide animal and financial loss data due to the defect. Lastly, we provide suggestions on how to minimize animal losses and be in accordance with the principles of the 3Rs (replacement, refinement, reduction). 相似文献
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6.
Vladimir I. Razinkov Grigory B. Melikyan Richard M. Epand Raquel F. Epand Fredric S. Cohen 《The Journal of general physiology》1998,112(4):409-422
Cells expressing the hemagglutinin protein of influenza virus were fused to planar bilayer membranes containing the fluorescent lipid probes octadecylrhodamine (R18) or indocarbocyanine (DiI) to investigate whether spontaneous curvature of each monolayer of a target membrane affects the growth of fusion pores.
R18 and DiI lowered the transition temperatures for formation of an inverted hexagonal phase, indicating that
these probes facilitate the formation of negative curvature structures. The probes are known to translocate from
one monolayer of a bilayer membrane to the other in a voltage-dependent manner. The spontaneous curvature of
the cis monolayer (facing the cells) or the trans monolayer could therefore be made more negative through control of the polarity of voltage across the planar membrane. Electrical admittance measurements showed that the
open times of flickering fusion pores were shorter when probes were in trans monolayers and longer when in cis
monolayers compared with times when probe was symmetrically distributed. Open times were the same for probe
symmetrically distributed as when probes were not present. Thus, open times were a function of the asymmetry of
the spontaneous curvature between the trans and cis monolayers. Enriching the cis monolayer with a negative curvature probe reduced the probability that a small pore would fully enlarge, whereas enriching the trans monolayer
promoted enlargement. Lysophosphatidylcholine has positive spontaneous curvature and does not translocate.
When lysophosphatidylcholine was placed in trans leaflets of planar membranes, closing of fusion pores was rare.
The effects of the negative and positive spontaneous curvature probes do not support the hypothesis that a flickering pore closes from an open state within a hemifusion diaphragm (essentially a “flat” structure). Rather, such effects support the hypothesis that the membrane surrounding the open pore forms a three-dimensional hourglass
shape from which the pore flickers shut. 相似文献
7.
Naoyuki Kondo Mariana Marin Jeong Hwa Kim Tanay M. Desai Gregory B. Melikyan 《The Journal of biological chemistry》2015,290(10):6558-6573
Whether HIV-1 enters cells by fusing with the plasma membrane or with endosomes is a subject of active debate. The ability of HIV-1 to mediate fusion between adjacent cells, a process referred to as “fusion-from-without” (FFWO), shows that this virus can fuse with the plasma membrane. To compare FFWO occurring at the cell surface with HIV-cell fusion through a conventional entry route, we designed an experimental approach that enabled the measurements of both processes in the same sample. The following key differences were observed. First, a very small fraction of viruses fusing with target cells participated in FFWO. Second, whereas HIV-1 fusion with adherent cells was insensitive to actin inhibitors, post-CD4/coreceptor binding steps during FFWO were abrogated. A partial dependence of HIV-cell fusion on actin remodeling was observed in CD4+ T cells, but this effect appeared to be due to the actin dependence of virus uptake. Third, deletion of the cytoplasmic tail of HIV-1 gp41 dramatically enhanced the ability of the virus to promote FFWO, while having a modest effect on virus-cell fusion. Distinct efficiencies and actin dependences of FFWO versus HIV-cell fusion are consistent with the notion that, except for a minor fraction of particles that mediate fusion between the plasma membranes of adjacent cells, HIV-1 enters through an endocytic pathway. We surmise, however, that cell-cell contacts enabling HIV-1 fusion with the plasma membrane could be favored at the sites of high density of target cells, such as lymph nodes. 相似文献
8.
Kumaran Sivagnanam Vijaya GS Raghavan Manesh Shah Robert L Hettich Nathan C Verberkmoes Mark G Lefsrud 《Proteome science》2011,9(1):1-14
Background
Cytokinin is a plant hormone that plays a crucial role in several processes of plant growth and development. In recent years, major breakthroughs have been achieved in the elucidation of the metabolism, the signal perception and transduction, as well as the biological functions of cytokinin. An important activity of cytokinin is the involvement in chloroplast development and function. Although this biological function has already been known for 50 years, the exact mechanisms remain elusive.Results
To elucidate the effects of altered endogenous cytokinin content on the structure and function of the chloroplasts, chloroplast subfractions (stroma and thylakoids) from transgenic Pssu-ipt and 35S:CKX1 tobacco (Nicotiana tabacum) plants with, respectively, elevated and reduced endogenous cytokinin content were analysed using two different 2-DE approaches. Firstly, thykaloids were analysed by blue-native polyacrylamide gel electrophoresis followed by SDS-PAGE (BN/SDS-PAGE). Image analysis of the gel spot pattern thus obtained from thylakoids showed no substantial differences between wild-type and transgenic tobacco plants. Secondly, a quantitative DIGE analysis of CHAPS soluble proteins derived from chloroplast subfractions indicated significant gel spot abundance differences in the stroma fraction. Upon identification by MALDI-TOF/TOF mass spectrometry, these proteins could be assigned to the Calvin-Benson cycle and photoprotective mechanisms.Conclusion
Taken together, presented proteomic data reveal that the constitutively altered cytokinin status of transgenic plants does not result in any qualitative changes in either stroma proteins or protein complexes of thylakoid membranes of fully developed chloroplasts, while few but significant quantitative differences are observed in stroma proteins. 相似文献9.
Michelle de la Vega Mariana Marin Naoyuki Kondo Kosuke Miyauchi Yuri Kim Raquel F Epand Richard M Epand Gregory B Melikyan 《Retrovirology》2011,8(1):1-19
Background
Dendritic cells (DCs) are among the first cells to encounter HIV-1 and play important roles in viral transmission and pathogenesis. Immature DCs allow productive HIV-1 replication and long-term viral dissemination. The pro-inflammatory factor lipopolysaccharide (LPS) induces DC maturation and enhances the efficiency of DC-mediated HIV-1 transmission. Type I interferon (IFN) partially inhibits HIV-1 replication and cell-cell transmission in CD4+ T cells and macrophages. Tetherin is a type I IFN-inducible restriction factor that blocks HIV-1 release and modulates CD4+ T cell-mediated cell-to-cell transmission of HIV-1. However, the role of type I IFN and tetherin in HIV-1 infection of DCs and DC-mediated viral transmission remains unknown.Results
We demonstrated that IFN-alpha (IFNα)-induced mature DCs restricted HIV-1 replication and trans-infection of CD4+ T cells. Tetherin expression in monocyte-derived immature DCs was undetectable or very low. High levels of tetherin were transiently expressed in LPS- and IFNα-induced mature DCs, while HIV-1 localized into distinct patches in these DCs. Knockdown of induced tetherin in LPS- or IFNα-matured DCs modestly enhanced HIV-1 transmission to CD4+ T cells, but had no significant effect on wild-type HIV-1 replication in mature DCs. Intriguingly, we found that HIV-1 replication in immature DCs induced significant tetherin expression in a Nef-dependent manner.Conclusions
The restriction of HIV-1 replication and transmission in IFNα-induced mature DCs indicates a potent anti-HIV-1 response; however, high levels of tetherin induced in mature DCs cannot significantly restrict wild-type HIV-1 release and DC-mediated HIV-1 transmission. Nef-dependent tetherin induction in HIV-1-infected immature DCs suggests an innate immune response of DCs to HIV-1 infection. 相似文献10.
Thiago?GazoniEmail author Simone?L?Gruber Ana?PZ?Silva Olivia?GS?Araújo Hideki?Narimatsu Christine?Strüssmann Célio?FB?Haddad Sanae?Kasahara 《BMC genetics》2012,13(1):109