Actions of insulin in fat cells. Effects of low temperature, uncouplers of oxidative phosphorylation, and respiratory inhibitors.

When isolated rat epididymal fat cells were incubated with [125I]iodoinsulin for 5 min at 37 degrees, radioactivity accumulated in the plasma membrane fraction (Peak 1) and an unidentified particulate fraction (Peak 2) as reported previously (Kono, T., Robinson, F.W., and Sarver, J.A. (1975) J. Biol. Chem. 250, 7826-7835). This accumulation of radioactivity in Peak 2 (but not that in Peak 1) was greatly impaired when cells were incubated with iodoinsulin in the presence of a variety of metabolic inhibitors that reduce the cellular content of ATP. The reduction in the ATP level coincided with a disappearance of the stimulatory effects of insulin on sugar transport and the hormone-sensitive phosphodiesterase. In contrast, ATP depletion had no significant effects, at least during a 5-to 15-min incubation, on the intracellular water space and on the basal sugar transport and phosphodiesterase activities. When cells once depleted on ATP by treatment with 2,4-dinitrophenol (1 mM; 10 min) were washed and suspended in fresh buffer, the ATP level was recovered almost fully in 10 min. This recovery coincided with the restoration of responsiveness to insulin. When cells were incubated with [125I]iodoinsulin or insulin for 5 min at 15 degrees instead of 37 degrees, a negligible quantity of radioactivity accumulated in Peak 2 and insulin failed to activate sugar transport. In contrast, under the same conditions, radioactivity accumulated in Peak 1 and insulin stimulated phosphodiesterase considerably. These results suggest that ATP, or some other compound metabolically related to ATP, may be necessary for the actions of insulin on sugar transport and phosphodiesterase. ATP, or some other related compound, may also be necessary in the formation of the radioactive Peak 2, although the physiological function and cellular location of this peak are yet to be ascertained.     

LCI1, a Chlamydomonas reinhardtii plasma membrane protein,functions in active CO2 uptake under low CO2

In response to high CO₂ environmental variability, green algae, such as Chlamydomonas reinhardtii, have evolved multiple physiological states dictated by external CO₂ concentration. Genetic and physiological studies demonstrated that at least three CO₂ physiological states, a high CO₂ (0.5–5% CO₂), a low CO₂ (0.03–0.4% CO₂) and a very low CO₂ (< 0.02% CO₂) state, exist in Chlamydomonas. To acclimate in the low and very low CO₂ states, Chlamydomonas induces a sophisticated strategy known as a CO₂‐concentrating mechanism (CCM) that enables proliferation and survival in these unfavorable CO₂ environments. Active uptake of C_i from the environment is a fundamental aspect in the Chlamydomonas CCM, and consists of CO₂ and HCO₃^– uptake systems that play distinct roles in low and very low CO₂ acclimation states. LCI1, a putative plasma membrane C_i transporter, has been linked through conditional overexpression to active C_i uptake. However, both the role of LCI1 in various CO₂ acclimation states and the species of C_i, HCO₃^– or CO₂, that LCI1 transports remain obscure. Here we report the impact of an LCI1 loss‐of‐function mutant on growth and photosynthesis in different genetic backgrounds at multiple pH values. These studies show that LCI1 appears to be associated with active CO₂ uptake in low CO₂, especially above air‐level CO₂, and that any LCI1 role in very low CO₂ is minimal.     

Autolysis-mediated membrane vesicle formation in Bacillus subtilis

It is known that Bacillus subtilis releases membrane vesicles (MVs) during the SOS response, which is associated with cell lysis triggered by the PBSX prophage-encoded cell-lytic enzymes XhlAB and XlyA. In this study, we demonstrate that MVs are released under various stress conditions: sucrose fatty acid ester (SFE; surfactant) treatment, cold shock, starvation, and oxygen deficiency. B. subtilis possesses four major host-encoded cell wall-lytic enzymes (autolysins; LytC, LytD, LytE, and LytF). Deletions of the autolysin genes abolished autolysis and the consequent MV production under these stress conditions. In contrast, deletions of xhlAB and xlyA had no effect on autolysis-triggered MV biogenesis, indicating that autolysis is a novel and prophage-independent pathway for MV production in B. subtilis. Moreover, we found that the cell lysis induced by the surfactant treatment was effectively neutralized by the addition of exogenous purified MVs. This result suggests that the MVs can serve as a decoy for the cellular membrane to protect the living cells in the culture from membrane damage by the surfactant. Our results indicate a positive effect of B. subtilis MVs on cell viability and provide new insight into the biological importance of the autolysis phenomenon in B. subtilis.     

Mitochondria‐type GPAT is required for mitochondrial fusion

Glycerol‐3‐phosphate acyltransferase (GPAT) is involved in the first step in glycerolipid synthesis and is localized in both the endoplasmic reticulum (ER) and mitochondria. To clarify the functional differences between ER‐GPAT and mitochondrial (Mt)‐GPAT, we generated both GPAT mutants in C. elegans and demonstrated that Mt‐GPAT is essential for mitochondrial fusion. Mutation of Mt‐GPAT caused excessive mitochondrial fragmentation. The defect was rescued by injection of lysophosphatidic acid (LPA), a direct product of GPAT, and by inhibition of LPA acyltransferase, both of which lead to accumulation of LPA in the cells. Mitochondrial fragmentation in Mt‐GPAT mutants was also rescued by inhibition of mitochondrial fission protein DRP‐1 and by overexpression of mitochondrial fusion protein FZO‐1/mitofusin, suggesting that the fusion/fission balance is affected by Mt‐GPAT depletion. Mitochondrial fragmentation was also observed in Mt‐GPAT‐depleted HeLa cells. A mitochondrial fusion assay using HeLa cells revealed that Mt‐GPAT depletion impaired mitochondrial fusion process. We postulate from these results that LPA produced by Mt‐GPAT functions not only as a precursor for glycerolipid synthesis but also as an essential factor of mitochondrial fusion.     

The Ecological Perspective of Microbial Communities in Two Pairs of Competitive Hawaiian Native and Invasive Macroalgae

Marine macroalgae are known to harbor large populations of microbial symbionts, and yet, microbe symbiosis in invasive macroalgae remains largely unknown. In this study, we applied molecular methods to study microbial communities associated with two invasive algae Acanthophora spicifera and Gracilaria salicornia and the two native algae Gracilaria coronopifolia and Laurencia nidifica at spatial and temporal scales in Hawaiian coral reef ecosystems. Bacterial communities of both the invasive and native macroalgae displayed little spatial and temporal variations, suggesting consistent and stable bacterial associations with these macroalgae. Results of this study identified three types of bacterial populations: nonspecific (present in both algal and water samples); algae-specific (found in all algal species); and species-specific (only found in individual species). The bacterial diversity of invasive algae was lower than that of their native counterparts at phylum and species levels. Notably, the vast majority (71 %) of bacterial communities associated with the invasive algae G. salicornia were representatives of Cyanobacteria, suggesting a potential ecological significance of symbiotic Cyanobacteria.     

Analysis of Factors That Determine Weight Gain during Smoking Cessation Therapy

Cigarette smokers are generally known to gain weight after quitting smoking, and such weight gain is thought to contribute to the worsening of glucose tolerance. While smoking cessation therapy such as nicotine replacement is useful to minimize post-cessation weight gain, substantial gain occurs even during the therapy. The purpose of the present study was to identify factors associated with weight gain during smoking cessation therapy. We evaluated 186 patients(132 males and 54 females)who visited our outpatient clinic for smoking cessation, and successfully achieved smoking abstinence. We performed gender-adjusted regression analysis for the rate of BMI increase from the beginning of cessation to 3 months after initiation. Furthermore, we performed multivariate analysis to investigate factors that determine the BMI increase after smoking cessation. The mean BMI significantly (p<0.0001) increased from 23.5±3.6 kg/m² at the initial consultation to 23.9±3.8 kg/m² at 3 months after the start of therapy. There was no significant difference in the extent of BMI increase between nicotine patch and varenicline therapy groups. Factors significantly correlated with the %BMI increase at 3 months after the start of therapy were triglyceride (p = 0.0006, βa = 0.260), high-density lipoprotein cholesterol (p = 0.0386, βa = −0.168), daily cigarette consumption (p = 0.0385, βa = 0.154), and the Fagerström Test for Nicotine Dependence (FTND) score (p = 0.0060, βa = 0.203). Stepwise multivariate analysis demonstrated that triglyceride and the FTND score were the factors determining the post-cessation BMI increase and that the FTND score was the strongest one. The present study demonstrated that smokers with a high FTND score are more likely to gain weight during smoking cessation therapy. Thus, smokers with a high nicotine dependency may require intervention against weight gain in the cessation clinic.     

Human Leukocyte Antigen and Systemic Sclerosis in Japanese: The Sign of the Four Independent Protective Alleles,DRB1*13:02, DRB1*14:06, DQB1*03:01, and DPB1*02:01

ObjectiveSeveral studies on associations between human leukocyte antigen (HLA) allele frequencies and susceptibility to systemic sclerosis (SSc) have been reported. Anti-centromere antibodies (ACA) and anti-topoisomerase I antibodies (ATA) are found in SSc patients. Here, we sought to identify HLA alleles associated with SSc in Japanese, and explored their associations with SSc phenotypes including the presence of autoantibodies.MethodsAssociations of HLA-DRB1, DQB1, and DPB1 were analyzed in 463 Japanese SSc patients and 413 controls.ResultsWe found that DRB1*13:02 (P = 0.0011, Pc = 0.0319, odds ratio [OR] 0.46, 95% confidence interval [CI] 0.29–0.73), DRB1*14:06 (P = 6.60X10^-5, Pc = 0.0020, OR 0.05, 95%CI 0.01–0.41), DQB1*03:01 (P = 0.0009, Pc = 0.0150, OR 0.56, 95%CI 0.40–0.79), and DPB1*02:01 (P = 5.16X10^-6, Pc = 8.77X10^-5, OR 0.52, 95%CI 0.39–0.69) were protectively associated with SSc. In addition, these four alleles seemed to be independently associated with the protection against the susceptibility of SSc. On the other hand, we could not find predisposing alleles for overall SSc. With respect to SSc subsets, a tendency for these four alleles to be protectively associated was observed. However, there was a significant association between DRB1*01:01, DRB1*10:01, DQB1*05:01, and DPB1*04:02 and the susceptibility to SSc with ACA. On the other hand, the presence of DRB1*15:02, DQB1*06:01, DPB1*03:01, and DPB1*09:01 was associated with SSc with ATA.ConclusionThus, the present study has identified protective associations of the four HLA class II alleles with overall Japanese SSc and predisposing associations of HLA class II alleles with Japanese SSc subsets.     

Taxonomic review of the Sebastes vulpes complex (Scorpaenoidei: Sebastidae)

Ichthyological Research - A taxonomic review of the Sebastes vulpes complex (S. vulpes, S. zonatus and S. ijimae) established the existence of two valid species, Sebastes vulpes Döderlein in...