The Longitudinal Association From Obesity to Depression: Results From the 12‐year National Population Health Survey

Prior observational studies have investigated the association between obesity and depression but evidence remains weak and mixed. There has been a call for high‐quality longitudinal studies to elucidate the etiologic relationship from obesity to depression. The main objective of this study was therefore to investigate whether obesity was a risk factor for depression in a nationally representative sample followed for 12 years. Seven waves of data collection (1994–1995 to 2006–2007) were obtained from the National Population Health Survey (NPHS). Our analyses included 10,545 adults without depression at baseline. Past‐year major depression episode (MDE) was assessed from the Composite International Diagnostic Interview‐Short Form for Major Depression (CIDI‐SFMD). Obesity was estimated using baseline BMI from self‐reported weight and height (obesity: BMI ≥30 kg/m²). Kaplan–Meier survival curves were generated and Cox proportional hazard regression modeling was used to estimate the risk of MDE by obesity status, controlling for sociodemographic and health and lifestyle variables. We found that obesity at baseline did not significantly predict subsequent MDE in women (adjusted hazard ratio (AHR): 1.03, 95% confidence interval (CI) 0.84–1.26) and negatively predicted MDE in men (HR: 0.71, CI 0.51–0.98), after adjusting for important confounders. In summary, our findings suggest that obesity is a significant (negative) predictor of depression in adult men but not in women. These results moderate prior evidence supporting a positive link from obesity to depression.     

Bioclimatic analyses of distributions of a parasitoid Peristenus digoneutis and its host species Lygus spp. in Europe and North America

• 1 Peristenus digoneutis Loan is a parasitoid of Lygus plant bugs, which was successfully introduced from Europe into North America in the 1980s for controlling native Lygus populations. Surveys confirmed that P. digoneutis populations have become established throughout eastern North America and that the spread of the parasitoid continues. For unknown reasons, previous releases of P. digoneutis in Western Canada were not successful.
• 2 A bioclimate (climex ®; Hearne Scientific Software Pty Ltd, Australia) model for P. digoneutis in North America was developed, based on climate and ecological parameters, and then validated with actual distribution records. The current distribution of P. digoneutis in eastern North America was consistent with the predicted distribution. The model suggests that P. digoneutis will probably continue its spread westwards throughout the U.S.A. along the Great Lakes.
• 3 The southern distribution of P. digoneutis is expected to be limited by hot summer temperatures, whereas its northern range is limited by the number of Lygus host generations rather than cold stress.
• 4 Peristenus digoneutis has the potential to occur in the southern parts of the prairie ecozone of western Canada; however, Ecoclimatic Index values in the prairies indicate mainly marginal or unfavourable conditions, which may explain why earlier releases of P. digoneutis in Western Canada failed.

     

Palatability and efficacy to possums and rats of pest control baits containing bird repellents

Repellents used to reduce by-kill of birds during pest control must not compromise acceptance by target species. Two repellents combined, anthraquinone (AQ; 0.4 g kg^?1) and d-pulegone (DP; 1.0) did not reduce the palatability of blue-coloured carrot baits to laboratory rats (Rattus norvegicus); nor did DP (2.0). Green-coloured carrot baits coated with AQ, DP or AQ + DP were taken from bait stations by wild possums (Trichosurus vulpecula) and rats. Toxic (1080) bait coated with AQ (0.4) and peanut oil (0.1) had reduced palatability but was accepted by laboratory rats. However, laboratory rats did not consume enough baits coated with AQ and bacon, peanut butter, cinnamon or DP to be killed. Anthraquinone (0.4 or 0.8) plus cinnamon and DP (0.5) did not affect palatability or lethality to captive ship rats (R. rattus) or possums. Anthraquinone and DP as surface coatings on baits are therefore acceptable to possums and possibly rats, at concentrations that deter some bird species.     

The 80L5C4 epitope overlaps with the homophilic binding site of the cell adhesion molecule gp80 of Dictyostelium.

The monoclonal antibody (mAb) 80L5C4 is a potent inhibitor of the cell adhesion molecule gp80 of Dictyostelium discoideum. To map the exact location of the epitope recognized by mAb 80L5C4, overlapping hexapeptides were synthesized on plastic pins and the binding p6 mAb 80L5C4 to these peptides was monitored by enzyme-linked immunosorbent assay. The 80L5C4 epitope is mapped to a single hexapeptide sequence GYKLNV, which shares five amino acid residues with the octapeptide sequence YKLNVNDS involved in gp80 homophilic binding. Analogue studies indicate that the hydrophobic residues within this sequence are crucial for antigen recognition.     

A Thematic Approach to the History of Physiology

This paper is a brief report of an undergraduate course in the history of physiology. A specific area, the development of the concepts of the cardiovascular system, was examined chronologically through primary readings and laboratory exercises. As an unusual approach to a frequently ignored but important subject, it may be of interest to those concerned with teaching the history of science.     

Characterization of Shiga-like toxin I B subunit purified from overproducing clones of the SLT-I B cistron.

The cistron encoding the B subunit of Escherichia coli Shiga-like toxin I (SLT-I) was cloned under control of the tac promoter in the expression vector pKK223-3 and the SLT-I B subunit was expressed constitutively in a wild-type background and inducibly in a lacIq background. The B subunit was located in the periplasmic space, and less than 10% was found in the culture medium after 24 h incubation. Polymyxin B extracts contained as much as 160 micrograms of B subunit/ml of culture. B subunit was purified to homogeneity by ion-exchange chromatography followed by chromatofocusing. Cross-linking analysis of purified native B subunit showed that it exists as a pentamer. In gels containing 0.1% SDS the native protein dissociated into monomers. B subunit was found to have the same glycolipid-receptor-specificity as SLT-I holotoxin. Competitive binding studies showed that B subunit and holotoxin had the same affinity for the globotriosylceramide receptor. We conclude that this recombinant plasmid is a convenient source of large amounts of purified SLT-I B subunit, which could be used for biophysical and structural studies or as a natural toxoid.     

Exaggerated hypoxic pulmonary hypertension in endothelin B receptor-deficient rats

Mechanisms by which endothelin (ET)-1 mediates chronic pulmonary hypertension remain incompletely understood. Although activation of the ET type A (ET(A)) receptor causes vasoconstriction, stimulation of ET type B (ET(B)) receptors can elicit vasodilation or vasoconstriction. We hypothesized that the ET(B) receptor attenuates the development of hypoxic pulmonary hypertension and studied a genetic rat model of ET(B) receptor deficiency (transgenic sl/sl). After 3 wk of severe hypoxia, the transgenic sl/sl pulmonary vasculature lacked expression of mRNA for the ET(B) receptor and developed exaggerated pulmonary hypertension that was characterized by elevated pulmonary arterial pressure, diminished cardiac output, and increased total pulmonary resistance. Plasma ET-1 was fivefold higher in transgenic sl/sl rats than in transgenic controls. Although mRNA for prepro-ET-1 was not different, mRNA for ET-converting enzyme-1 was higher in transgenic sl/sl than in transgenic control lungs. Hypertensive lungs of sl/sl rats also produced less nitric oxide metabolites and 6-ketoprostaglandin F(1alpha), a metabolite of prostacyclin, than transgenic controls. These findings suggest that the ET(B) receptor plays a protective role in the pulmonary hypertensive response to chronic hypoxia.     

Propranolol metabolism by isolated hepatocytes from normal and cirrhotic rat livers: the effect of albumin

Several recent reports have shown that the hepatic uptake and subsequent elimination of some substrates is faster in the presence of albumin than in its absence, as if some of the substrate bound to albumin was also available for uptake. In the present study, we examined the effect of albumin on the clearance of propranolol by isolated rat hepatocyte suspensions. The clearance of total drug decreased progressively as albumin concentration increased. There was also a progressive decrease in the free fraction of propranolol and the net result was an increase in the clearance of unbound drug (+50% at 40 g/L albumin). This increase was not due to an oncotic pressure effect of albumin, nor to the presence of fatty acids bound to albumin. The clearance of propranolol by isolated hepatocytes from cirrhotic rats was decreased compared with controls (-50%), and albumin also increased propranolol free clearance, albeit to a lesser extent than in control animals. Our results indicate that albumin facilitates the elimination of propranolol by hepatocytes, possibly because of surface-mediated catalysis of the albumin-propranolol complexes.