K+/H+ antiport in mitochondria

Mitochondria contain a latent K⁺/H⁺ antiporter that is activated by Mg²⁺-depletion and shows optimal activity in alkaline, hypotonic suspending media. This K⁺/H⁺ antiport activity appears responsible for a respiration-dependent extrusion of endogenous K⁺, for passive swelling in K⁺ acetate and other media, for a passive exchange of matrix⁴²K⁺ against external K⁺, Na⁺, or Li⁺, and for the respiration-dependent ion extrusion and osmotic contraction of mitochondria swollen passively in K⁺ nitrate. K⁺/H⁺ antiport is inhibited by quinine and by dicyclohexylcarbodiimide when this reagent is reacted with Mg²⁺-depleted mitochondria. There is good suggestive evidence that the K⁺/H⁺ antiport may serve as the endogenous K⁺-extruding device of the mitochondrion. There is also considerable experimental support for the concept that the K⁺/H⁺ antiport is regulated to prevent futile influx-efflux cycling of K⁺. However, it is not yet clear whether such regulation depends on matrix free Mg²⁺, on membrane conformational changes, or other as yet unknown factors.     

Human microvascular endothelial cell-extracellular matrix interaction in cellular growth state determination

We introduce two methods, both of which are based on cellular-extracellular matrix interaction, which will facilitate the study of human microvascular endothelial cells. One method describes the means to obtain a G1 population baseline in human microvasclular endothelial cells. Because of the contribution of the extracellular matrix in endothelial cell growth, synchronization in G1 was possible only after the incorporation of angiostatic levels of heparin and hydrocortisone into the extracellular matrix. In the second method, we demonstrate that selective perturbation of human microvascular endothelial cell-extracellular matrix interactions results in the induction of a transitional growth state, between proliferative and differentiated growth states, in human microvascular endothelial cells. In the functional, microtubule formation assays, transitional growth state endothelial cells display rates that are indermediate between those obtained from differentiated and proliferative endothelial cells. Our results demonstrate the importance of the human microvascular endothelial cell-extracellular matrix interaction in the determination of cellular growth state. Our findings also imply that responsiveness of microvascular endothelial cells to their cellular-extracellular matrix environs is highest during the differentiated growth state.     

Bioremediation of metal‐contaminated surface and groundwaters

Microorganisms immobilize, mobilize, or transform metals by extracellular precipitation reactions, intracellular accumulation, oxidation and reduction reactions, methylation and demethylation, and extracellular binding and complexation. Nearly all of these microbe/metal interactions occur within the wetlands approach to acid mine drainage treatment, a process that is rapidly gaining support as a low‐maintenance, cost‐effective approach to solving an important environmental problem. Several proprietary processes, which employ nonliving microorganisms that are immobilized in polymer matrixes, are entering the water treatment market. These processes take advantage of negatively charged functional groups on cell walls and exopolymers of microorganisms that bind cationic metals. These biosorbents effectively remove low concentrations (<1 to about 20 mg/L) of heavy metal cations in the presence of high concentrations of alkaline earth metals (Ca²⁺ and Mg²⁺) and organic contaminants to levels lower than the U.S. National Drinking Water Standards. Immobilization of the biomass in polymer matrixes yields products that have substantial chemical and mechanical integrity. These immobilized products lend themselves to application in conventionally engineered systems such as up‐flow and down‐flow columns, expanded‐bed systems, dispersed‐bed systems, and low‐maintenance trough systems. Biosorption will probably play an important role in achieving the strict environmental standards now being enforced.     

Marked seasonal variation in the wild mouse gut microbiota

Recent studies have provided an unprecedented view of the microbial communities colonizing captive mice; yet the host and environmental factors that shape the rodent gut microbiota in their natural habitat remain largely unexplored. Here, we present results from a 2-year 16 S ribosomal RNA gene sequencing-based survey of wild wood mice (Apodemus sylvaticus) in two nearby woodlands. Similar to other mammals, wild mice were colonized by 10 bacterial phyla and dominated by the Firmicutes, Bacteroidetes and Proteobacteria. Within the Firmicutes, the Lactobacillus genus was most abundant. Putative bacterial pathogens were widespread and often abundant members of the wild mouse gut microbiota. Among a suite of extrinsic (environmental) and intrinsic (host-related) factors examined, seasonal changes dominated in driving qualitative and quantitative differences in the gut microbiota. In both years examined, we observed a strong seasonal shift in gut microbial community structure, potentially due to the transition from an insect- to a seed-based diet. This involved decreased levels of Lactobacillus, and increased levels of Alistipes (Bacteroidetes phylum) and Helicobacter. We also detected more subtle but statistically significant associations between the gut microbiota and biogeography, sex, reproductive status and co-colonization with enteric nematodes. These results suggest that environmental factors have a major role in shaping temporal variations in microbial community structure within natural populations.     

Functional consequences of human immunodeficiency virus escape from an HLA-B*13-restricted CD8+ T-cell epitope in p1 Gag protein

The observed association between HLA-B*13 and control of human immunodeficiency virus type 1 (HIV-1) infection has been linked to the number of Gag-specific HLA-B*13-restricted cytotoxic T-cell (CTL) responses identified. To date, the Gag escape mutations described that result in an in vitro fitness cost to the virus have been located within structural protein p24 only. Here we investigated the hypothesis that CTL escape mutations within other regions of HIV Gag may also reduce viral fitness and contribute to immune control. We analyzed an HLA-B*13-restricted CTL response toward an epitope in p1 Gag, RQANFLGKI_429-437 (RI9), where amino acid variation at Gag residues 436 and 437 is associated with HLA-B*13 expression. In this work, we assessed the impact of amino acid substitutions at these positions on CTL recognition and on HIV-1 fitness. We demonstrated that substitutions I437L and I437M largely abrogate CTL recognition and reduce viral fitness while variants K436R and I437V have only a marginal effect on recognition and fitness. Examination of the patterns of protein synthesis indicated that the loss of fitness in the I437L and I437M mutants is associated with the accumulation of unprocessed Gag precursors. A significant reduction in ribosomal frameshifting efficiency was observed with I437M, suggesting that this mechanism contributes to the observed reduced fitness of this virus. These studies illustrate the apparent trade-off available to the virus between evasion of CTL recognition in p1 Gag and the functional consequences for viral fitness.     

The Impact of Thyroid Cancer and Post-Surgical Radioactive Iodine Treatment on the Lives of Thyroid Cancer Survivors: A Qualitative Study

Background

Adjuvant treatment with radioactive iodine (RAI) is often considered in the treatment of well-differentiated thyroid carcinoma (WDTC). We explored the recollections of thyroid cancer survivors on the diagnosis of WDTC, adjuvant radioactive iodine (RAI) treatment, and decision-making related to RAI treatment. Participants provided recommendations for healthcare providers on counseling future patients on adjuvant RAI treatment.

Methods

We conducted three focus group sessions, including WDTC survivors recruited from two Canadian academic hospitals. Participants had a prior history of WDTC that was completely resected at primary surgery and had been offered adjuvant RAI treatment. Open-ended questions were used to generate discussion in the groups. Saturation of major themes was achieved among the groups.

Findings

There were 16 participants in the study, twelve of whom were women (75%). All but one participant had received RAI treatment (94%). Participants reported that a thyroid cancer diagnosis was life-changing, resulting in feelings of fear and uncertainty. Some participants felt dismissed as not having a serious disease. Some participants reported receiving conflicting messages from healthcare providers on the appropriateness of adjuvant RAI treatment or insufficient information. If RAI-related side effects occurred, their presence was not legitimized by some healthcare providers.

Conclusions

The diagnosis and treatment of thyroid cancer significantly impacts the lives of survivors. Fear and uncertainty related to a cancer diagnosis, feelings of the diagnosis being dismissed as not serious, conflicting messages about adjuvant RAI treatment, and treatment-related side effects, have been raised as important concerns by thyroid cancer survivors.