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181.
182.
Water quality and algal populations in the Vaal River Barrage Reservoir have been monitored extensively for many decades, because of its importance as a water source for the most densely populated area in South Africa. Although Aulacoseira granulata (Ehrenberg) Simonsen is frequently found and at it times dominates algal assemblages in the Barrage, Aulacoseira ambigua (F.Meister) Tuji & D.M.Williams has never before been recorded at this locality. During a countrywide proficiency-testing scheme for algae counting, coordinated by Rand Water, spiral-shaped diatom colonies with distinctly curved cells were detected during May 2015. Upon investigation, it was found that the spiral colonies were Aulacoseira ambigua f. japonica, its presence in the fresh waters of South Africa being recorded for the first time. Since their first appearance during May 2015, colonies of Aulacoseira ambigua f. japonica have been constantly present in the surface waters of the Barrage. Their presence at this site can be linked to increasing eutrophication in the Vaal River, because the spiral form is known to prefer eutrophic conditions. Centric diatoms rarely form spiral colonies and there is some confusion in the literature as to the identity of this particular form, therefore in this paper we discuss this taxon, its nomenclature and ecological significance. 相似文献
183.
The G-protein-gated inwardly rectifying K
+(GIRK) family of ion channels form functional Gβγ-sensitive channels as heteromultimers of GIRK1 and either the GIRK2 or GIRK4
subunits. However, the homologous mouse brain GIRK3 clone failed to express in the earliest reported functional experiments
in Xenopus oocytes. We recloned the GIRK3 subunit from mouse brain and found that the new clone differed significantly from that originally
reported. The functional aspects of GIRK3 were reinvestigated by expression in CHO cells. The single channel properties of
GIRK1/GIRK3 were characterized and compared to those of the GIRK1/GIRK2 and GIRK1/GIRK4 channels. All three GIRK1/GIRKx combinations
produced channels with nearly indistinguishable conductances and kinetics. The response of GIRK1/GIRK3 to Gβγ in the 1–47
nm range was examined and found to be indistinguishable from that of GIRK1/GIRK4 channels. We conclude that GIRK1, with either
GIRK2, 3, or 4, gives rise to heteromultimeric channels with virtually identical conductances, kinetics, and Gβγ sensitivities.
Received: 13 January 1999/Revised: 2 March 1999 相似文献
184.
Duenas-Decamp MJ Peters PJ Repik A Musich T Gonzalez-Perez MP Caron C Brown R Ball J Clapham PR 《Future virology》2010,5(4):435-451
HIV-1 R5 viruses predominantly use CCR5 as a coreceptor to infect CD4(+) T cells and macrophages. While R5 viruses generally infect CD4(+) T cells, research over the past few years has demonstrated that they vary extensively in their capacity to infect macrophages. Thus, R5 variants that are highly macrophage tropic have been detected in late disease and are prominent in brain tissue of subjects with neurological complications. Other R5 variants that are less sensitive to CCR5 antagonists and use CCR5 differently have also been identified in late disease. These latter variants have faster replication kinetics and may contribute to CD4 T-cell depletion. In addition, R5 viruses are highly variable in many other properties, including sensitivity to neutralizing antibodies and inhibitors that block HIV-1 entry into cells. Here, we review what is currently known about how HIV-1 R5 viruses vary in cell tropism and other properties, and discuss the implications of this variation on transmission, pathogenesis, therapy and vaccines. 相似文献
185.
186.
The recent discovery of genes encoding the mitochondrial calcium (Ca2+) uniporter has revealed new opportunities for studying how abnormal Ca2+ signals cause disease. Ca2+ transport across the mitochondrial inner membrane is highly regulated, and the uniporter is the channel that acts as a major portal for Ca2+ influx. Low amounts of mitochondrial Ca2+ can boost ATP synthesis, but excess amounts, such as following cytoplasmic Ca2+ overload in heart failure, triggers mitochondrial failure and cell death. In fact, precisely because mitochondrial Ca2+ transport is so tightly regulated, a fundamental understanding of how the uniporter functions is necessary. Two key uniporter features allow Ca2+ influx without mitochondrial damage during normal physiology. First, the channel is significantly more selective than other known Ca2+ channels. This prevents the permeation of other ions and uncoupling of the electrochemical gradient. Second, the uniporter becomes active at only high Ca2+ concentrations, preventing a resting leak of cytoplasmic Ca2+ itself. Now possessing the identities of the various proteins forming the uniporter, we can proceed with efforts to define the molecular determinants of permeation, selectivity and Ca2+-regulation. 相似文献
187.
Ming-Feng Tsai Dawei Jiang Linlin Zhao David Clapham Christopher Miller 《The Journal of general physiology》2014,143(1):67-73
The leucine zipper, EF hand–containing transmembrane protein 1 (Letm1) gene encodes a mitochondrial inner membrane protein, whose depletion severely perturbs mitochondrial Ca2+ and K+ homeostasis. Here we expressed, purified, and reconstituted human Letm1 protein in liposomes. Using Ca2+ fluorophore and 45Ca2+-based assays, we demonstrate directly that Letm1 is a Ca2+ transporter, with apparent affinities of cations in the sequence of Ca2+ ≈ Mn2+ > Gd3+ ≈ La3+ > Sr2+ >> Ba2+, Mg2+, K+, Na+. Kinetic analysis yields a Letm1 turnover rate of 2 Ca2+/s and a Km of ∼25 µM. Further experiments show that Letm1 mediates electroneutral 1 Ca2+/2 H+ antiport. Letm1 is insensitive to ruthenium red, an inhibitor of the mitochondrial calcium uniporter, and CGP-37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger. Functional properties of Letm1 described here are remarkably similar to those of the H+-dependent Ca2+ transport mechanism identified in intact mitochondria. 相似文献
188.
Non-macrophage-tropic human immunodeficiency virus type 1 R5 envelopes predominate in blood, lymph nodes, and semen: implications for transmission and pathogenesis
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Peters PJ Sullivan WM Duenas-Decamp MJ Bhattacharya J Ankghuambom C Brown R Luzuriaga K Bell J Simmonds P Ball J Clapham PR 《Journal of virology》2006,80(13):6324-6332
Human immunodeficiency virus type 1 (HIV-1) R5 isolates that predominantly use CCR5 as a coreceptor are frequently described as macrophage tropic. Here, we compare macrophage tropism conferred by HIV-1 R5 envelopes that were derived directly by PCR from patient tissue. This approach avoids potentially selective culture protocols used in virus isolation. Envelopes were amplified (i) from blood and semen of adult patients and (ii) from plasma of pediatric patients. The phenotypes of these envelopes were compared to those conferred by an extended panel of envelopes derived from brain and lymph node that we reported previously. Our results show that R5 envelopes vary by up to 1,000-fold in their capacity to confer infection of primary macrophages. Highly macrophage-tropic envelopes were predominate in brain but were infrequent in semen, blood, and lymph node samples. We also confirmed that the presence of N283 in the C2 CD4 binding site of gp120 is associated with HIV-1 envelopes from the brain but absent from macrophage-tropic envelopes amplified from blood and semen. Finally, we compared infection of macrophages, CD4(+) T cells, and peripheral blood mononuclear cells (PBMCs) conferred by macrophage-tropic and non-macrophage-tropic envelopes in the context of full-length replication competent viral clones. Non-macrophage-tropic envelopes conferred low-level infection of macrophages yet infected CD4(+) T cells and PBMCs as efficiently as highly macrophage-tropic brain envelopes. The lack of macrophage tropism for the majority of the envelopes amplified from lymph node, blood, and semen is striking and contrasts with the current consensus that R5 primary isolates are generally macrophage tropic. The extensive variation in R5 tropism reported here is likely to have an important impact on pathogenesis and on the capacity of HIV-1 to transmit. 相似文献
189.
Turmeric (Curcuma longa L.) is an important spice crop plant that is sterile and cannot be improved by conventional breeding. An efficient method
for stable transformation for turmeric, C. longa L., was developed using particle bombardment. Callus cultures initiated from shoots were bombarded with gold particles coated
with plasmid pAHC25 containing the bar and gusA genes each driven by the maize ubiquitin promoter. Transformants were selected on medium containing glufosinate. Transgenic
lines were established on selection medium from 50% of the bombarded calluses. Transgenic shoots regenerated from these were
multiplied and stably transformed plantlets were produced. Polymerase chain reaction (PCR) and histochemical GUS assay confirmed
the stable transformation. Transformed plantlets were resistant to glufosinate. 相似文献
190.
Smith PL Maloney KN Pothen RG Clardy J Clapham DE 《The Journal of biological chemistry》2006,281(40):29897-29904
Many transient receptor potential (TRP) channels are activated or blocked by various compounds found in plants; two prominent examples include the activation of TRPV1 channels by capsaicin and the activation of TRPM8 channels by menthol. We sought to identify additional plant compounds that are active on other types of TRP channels. We screened a library of extracts from 50 Chinese herbal plants using a calcium-imaging assay to find compounds active on TRPV3 and TRPV4 channels. An extract from the plant Andrographis paniculata potently activated TRPV4 channels. The extract was fractionated further, and the active compound was identified as bisandrographolide A (BAA). We used purified compound to characterize the activity of BAA on certain TRPV channel subtypes. Although BAA activated TRPV4 channels with an EC(50) of 790-950 nm, it did not activate or block activation of TRPV1, TRPV2, or TRPV3 channels. BAA activated a large TRPV4-like current in immortalized mouse keratinocytes (308 cells) that have been shown to express TRPV4 protein endogenously. This compound also activated TRPV4 currents in cell-free outside-out patches from HEK293T cells overexpressing TRPV4 cDNA, suggesting that BAA can activate the channel in a membrane-delimited manner. Another related compound, andrographolide, found in abundance in the plant Andrographis was unable to activate or block activation of TRPV4 channels. These experiments show that BAA activates TRPV4 channels, and we discuss the possibility that activation of TRPV4 by BAA could play a role in some of the effects of Andrographis extract described in traditional medicine. 相似文献