Shift Work and Obesity among Canadian Women: A Cross-Sectional Study Using a Novel Exposure Assessment Tool

Background/Objectives

It has been suggested that the association between shift work and chronic disease is mediated by an increase in obesity. However, investigations of the relationship between shift work and obesity reveal mixed findings. Using a recently developed exposure assessment tool, this study examined the association between shift work and obesity among Canadian women from two studies: a cohort of university alumni, and a population-based study.

Methods

Self-administered questionnaire data were used from healthy, currently employed females in a population-based study, the Ontario Women’s Diet and Health case-control study (n = 1611 controls), and from a subset of a of university alumni from the Canadian Study of Diet, Lifestyle, and Health (n = 1097) cohort study. Overweight was defined as BMI≥25 to <30, and obesity as BMI≥30. Reported occupation was converted to occupational codes and linked to a probability of shift work value derived from Survey of Labour and Income Dynamics data. Regular evenings, nights, or rotating work comprised shift work. Polytomous logistic regression estimated the association between probability of shift work, categorized as near nil, low, medium, and high probability of shift work, on overweight and obesity, controlling for detected confounders.

Results

In the population-based sample, high probability of shift work was associated with obesity (reference = near nil probability of shift work, OR: 1.88, 95% CI: 1.01–3.51, p = 0.047). In the alumni cohort, no significant association was detected between shift work and overweight or obesity.

Conclusions

As these analyses found a positive association between high probability of shift work exposure and obesity in a population-based sample, but not in an alumni cohort, it is suggested that the relationship between shift work and obesity is complex, and may be particularly susceptible to occupational and education-related factors within a given population.     

Regulation of Argonaute Slicer Activity by Guide RNA 3′ End Interactions with the N-terminal Lobe

Structural studies indicate that binding of both the guide RNA (siRNA and miRNA) and the target mRNA trigger substantial conformational changes in the Argonaute proteins. Here we explore the role of the N-terminal lobe (and its PAZ domain) in these conformational changes using biochemical and cell culture-based approaches. In vitro, whereas deletion (or mutation) of the N-terminal lobe of DmAgo1 and DmAgo2 had no effect on binding affinity to guide RNAs, we observed a loss of protection of the 3′ end of the guide RNA and decreased target RNA binding; consistent with this, in cells, loss of function DmAgo1 PAZ variant proteins (PAZ6 and ΔN-PAZ) still bind RNA, although the RNAs are shorter than normal. We also find that deletion of the N-terminal lobe results in constitutive activation of endogenous PIWI domain-based cleavage activity in vitro, providing insights into how cleavage activity may be regulated in vivo in response to different types of pairing interactions with the target mRNAs.     

Effect of the rumen ciliates Entodinium caudatum, Epidinium ecaudatum and Eudiplodinium maggii, and combinations thereof, on ruminal fermentation and total tract digestion in sheep

The quantitative importance of individual ciliate species and their interaction in the rumen is still unclear. The present study was performed to test whether there are species differences in the influence on ruminal fermentation in vivo and if combinations of ciliates act additive in that respect. Six adult wethers fed a hay-concentrate diet were defaunated, then refaunated either with Entodinium caudatum (EC), Epidinium ecaudatum (EE) or Eudiplodinium maggii (EM) alone, then progressively with all possible species combinations. Feed, faeces, urine, ruminal fluid and gas were sampled for eight days always after at least 21 days of adaptation. With a linear mixed model, accounting for the 2 x 2 x 2 full factorial study design, mean marginal effect sizes, i.e., the magnitude of change in variables as caused by the presence of each ciliate species or of combinations of them, were estimated. The apparent digestibility of organic matter and neutral detergent fibre remained unaffected. The apparent N digestibility increased by 0.054 with EM (0.716 with defaunation). Ruminal ammonia increased by 1.6, 4.0 and 8.7 mmol/l in the presence of EM, EC and EE, respectively, compared to defaunation (6.9 mmol/l). In the EM + EE combination, ruminal ammonia was lower than would have been expected from an additive effect. With EE, total short-chain fatty acids increased by 23 mmol/l (100 mmol/l with defaunation), but not when EE was combined with EM. The acetate-to-propionate ratio decreased by 0.73 units in the presence of EE (4.0 with defaunation), but only when EE was the sole ciliate species in the rumen. In the presence of any ciliate species, the 16S rDNA copies of total Bacteria and major fibrolytic species decreased to 0.52- and 0.22-fold values, respectively of that found without protozoa. Total Archaea were unaffected; however, Methanobacteriales copies increased 1.44-fold with EC. The CH4-to-CO2 ratio of ruminal gas decreased by 0.036 with EM and 0.051 with EE (0.454 with defaunation). In conclusion, individual ciliates affected ruminal fermentation differently and, when different species were combined, sometimes in a non-additive manner. From the ciliates investigated, EE affected ruminal fermentation most and might play a dominant role in mixed ciliate populations.     

Regional Characteristics of Histamine Uptake into Neonatal Rat Astrocytes

Histaminergic signalling constitutes an attractive target for treatment of neuropsychiatric disorders. One obstacle to developing new pharmacological options has been failure to identify putative specific histamine transporter responsible for histamine clearance. Although high-affinity histamine uptake was detected in neonatal cortical astrocytes, its existence in other brain regions remains largely unexplored. We investigated whether cerebellar and striatal astrocytes participate in histamine clearance and evaluated the role of organic cation transporters (OCT) in astroglial histamine transport. Kinetic and pharmacological characteristics of histamine transport were determined in cultured astrocytes derived from neonatal rat cerebellum, striatum and cerebral cortex. As well as astrocytes of cortical origin, cultured striatal and cerebellar astrocytes displayed temperature-sensitive, high-affinity histamine uptake. Exposure to ouabain or Na⁺-free medium, supplemented with choline chloride markedly depressed histamine transport in cortical astrocytes. Conversely, histamine uptake in striatal and cortical astrocytes was ouabain-resistant and was only partially diminished during incubation in the absence of Na⁺. Also, histamine uptake remained unaltered upon exposure to OCT inhibitor corticosterone, although OCTs were expressed in cultured astrocytes. Finally, histamine transport in cerebellar and striatal astrocytes was not sensitive to antidepressants. Despite common characteristics, cerebellar astrocytes had lower affinity, but markedly higher transport capacity for histamine compared to striatal astrocytes. Collectively, we provide evidence to suggest that cerebellar, striatal as well as cortical astrocytes possess saturable histamine uptake systems, which are not operated by OCTs. In addition, our data indicate that Na⁺-independent histamine carrier predominates in cerebellar and striatal astrocytes, whereas Na⁺-dependent transporter underlies histamine uptake in cortical astrocytes. Our findings implicate a role for histamine transporters in regulation of extracellular histamine concentration in cerebellum and striatum. Inhibition of histamine uptake might represent a viable option to modulate histaminergic neurotransmission.     

A novel tetravalent bispecific TandAb (CD30/CD16A) efficiently recruits NK cells for the lysis of CD30+ tumor cells

To improve recruitment and activation of natural killer (NK) cells to lyse tumor cells, we isolated a human anti-CD16A antibody with similar affinity for the CD16A 158F/V allotypes, but no binding to the CD16B isoform. Using CD16A-targeting Fv domains, we constructed a tetravalent bispecific CD30/CD16A tandem diabody (TandAb®) consisting solely of Fv domains. This TandAb has two binding sites for CD16A and two for CD30, the antigen identifying Hodgkin lymphoma cells. The binding and cytotoxicity of the TandAb were compared with antibodies with identical anti-CD30 domains: (1) a native IgG, (2) an IgG optimized for binding to Fc receptors, and (3) a bivalent bispecific CD30/CD16A diabody. Due to its CD16A-bivalency and reduced k_off, the TandAb was retained longer on the surface of NK cells than the IgGs or the diabody. This contributed to the higher potency and efficacy of the TandAb relative to those of the other anti-CD30 antibodies. TandAb cytotoxicity was independent of the CD16A allotype, whereas the anti-CD30 IgGs were substantially less cytotoxic when NK cells with low affinity CD16A allotype were employed. TandAb activation of NK cells was strictly dependent on the presence of CD30⁺ target cells. Therefore, the CD30/CD16A TandAb may represent a promising therapeutic for the treatment of Hodgkin’s lymphoma; further, anti-CD16A TandAbs may function as potent immunotherapeutics that specifically recruit NK cells to destroy cancer cells.     

Optimization and evolution of light harvesting in photosynthesis: the role of antenna chlorophyll conserved between photosystem II and photosystem I

The efficiency of oxygenic photosynthesis depends on the presence of core antenna chlorophyll closely associated with the photochemical reaction centers of both photosystem II (PSII) and photosystem I (PSI). Although the number and overall arrangement of these chlorophylls in PSII and PSI differ, structural comparison reveals a cluster of 26 conserved chlorophylls in nearly identical positions and orientations. To explore the role of these conserved chlorophylls within PSII and PSI we studied the influence of their orientation on the efficiency of photochemistry in computer simulations. We found that the native orientations of the conserved chlorophylls were not optimal for light harvesting in either photosystem. However, PSII and PSI each contain two highly orientationally optimized antenna chlorophylls, located close to their respective reaction centers, in positions unique to each photosystem. In both photosystems the orientation of these optimized bridging chlorophylls had a much larger impact on photochemical efficiency than the orientation of any of the conserved chlorophylls. The differential optimization of antenna chlorophyll is discussed in the context of competing selection pressures for the evolution of light harvesting in photosynthesis.     

Gas-phase molecular structures of substituted 1,3-bisketenes: A challenge for theory and experiment

Molecular structures of dimethylbis(trimethylsilylketyl)silane (Me₂Si[C(SiMe₃)CO]₂), dimethylbis(trimethylgermylketyl)silane (Me₂Si[C(GeMe₃)CO]₂), and dimethylbis(trimethylstannylketyl)germane (Me₂Ge[C(SnMe₃)CO]₂) have been studied in the gas phase by electron diffraction accompanied by high level ab initio and DFT calculations. Extensive theoretical conformational analyses of the molecules in the vapour predicted a possibility of existence of two types of conformers with small energy differences. The first type had gauche-gauche arrangements of the ketenyl groups in the central C(CO)XC(CO) fragments directed away from each other. The second type had nearly syn-gauche arrangements of the ketenyl groups. In addition, the energy differences were found to depend on the level of computations used. The experimental analysis, in turn, was unable to distinguish between different conformers due to the large number of similar overlapping distances. The experimental data were fitted by an averaged single-conformer model, which nevertheless allowed reliable determination of bonds and bonded angles in the molecules. Main experimental (r_h1) structural parameters for Me₂Si[C(SiMe₃)CO]₂, Me₂Si[C(GeMe₃)CO]₂, and Me₂Ge[C(SnMe₃)CO]₂, i.e. Me₂X[C(YMe₃)CO]₂ (X,Y = Si, Ge, Sn), are (X-C)_mean 187.7(1) pm, 194.6(2) pm, 216.1(3) pm; (Y-C)_mean, 187.7(1) pm, 188.8(8) pm, 194.6(4) pm; (CC)_mean, 135.3(5) pm, 131.6(5) pm, 131.5(13) pm; (CO)_mean, 117.0(7) pm, 117.4(7) pm, 119.0(11) pm; (C-H)_mean, 110.6(7) pm, 110.0(4) pm, 109.1(13) pm; (X(Y)-CC)_mean, 114.4(2)°, 115.6(1)°, 115.6(2)°; (C-X(Y)-C_Me)_mean, 108.3(3)°, 108.4(3)°, 108.9(13)°; C(2)-C(1)-Y(4)-C(10), −19(6)°, 5(4)°, −9(10)°; C(7)-C(6)-Y(9)-C(38),−22(7)°, −32(3)°, −9(10)°; C(2)-C(1)-X(5)-C(6), 128(4)°, 142(1)°, 108(9)°; C(7)-C(6)-X(5)-C(1), 92(6)°, 115(2)°, 108(9)°, respectively.     

Regulation of the distribution of chlorophyll and phycobilin-absorbed excitation energy in cyanobacteria. A structure-based model for the light state transition

The light state transition regulates the distribution of absorbed excitation energy between the two photosystems (PSs) of photosynthesis under varying environmental conditions and/or metabolic demands. In cyanobacteria, there is evidence for the redistribution of energy absorbed by both chlorophyll (Chl) and by phycobilin pigments, and proposed mechanisms differ in the relative involvement of the two pigment types. We assayed changes in the distribution of excitation energy with 77K fluorescence emission spectroscopy determined for excitation of Chl and phycobilin pigments, in both wild-type and state transition-impaired mutant strains of Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803. Action spectra for the redistribution of both Chl and phycobilin pigments were very similar in both wild-type cyanobacteria. Both state transition-impaired mutants showed no redistribution of phycobilin-absorbed excitation energy, but retained changes in Chl-absorbed excitation. Action spectra for the Chl-absorbed changes in excitation in the two mutants were similar to each other and to those observed in the two wild types. Our data show that the redistribution of excitation energy absorbed by Chl is independent of the redistribution of excitation energy absorbed by phycobilin pigments and that both changes are triggered by the same environmental light conditions. We present a model for the state transition in cyanobacteria based on the x-ray structures of PSII, PSI, and allophycocyanin consistent with these results.