Sexual Functioning and Obesity: A Review

We review the literature on the relationship between obesity and sexual functioning. Eleven population‐based studies, 20 cross‐sectional non‐population‐based studies, and 16 weight loss studies are reviewed. The consistency of findings suggests that the relationship between obesity and reduced sexual functioning is robust, despite diverse methods, instruments, and settings. In most population‐based studies, erectile dysfunction (ED) is more common among obese men than among men of recommended weight. Studies of patients in clinical settings often include individuals with higher degrees of obesity, with most studies showing a relationship between obesity and lower levels of sexual functioning, especially ED. The few studies that include both genders generally report more problems among women. Most studies of patients with comorbidities associated with obesity also find an association between obesity and reduced sexual functioning. Most weight loss studies demonstrate improvement in sexual functioning concurrent with weight reduction despite varying study designs, weight loss methods, and follow‐up periods. We recommend that future studies (i) investigate differences and similarities between men and women with respect to obesity and sexual functioning, (ii) use instruments that go beyond the assessment of sexual dysfunction to include additional concepts such as sexual satisfaction, interest, and arousal and, (iii) assess how and the degree to which obese individuals are affected by sexual difficulties. Given the high prevalence of obesity and the inverse association between body mass and sexual functioning, we also recommend that sexual functioning should be more fully addressed by clinicians, both in general practice and in weight loss programs.     

Up,up, and away: relative importance of horizontal and vertical escape from predators for survival and senescence

Animals fleeing a potential predator can escape horizontally or vertically, although vertical flight is more expensive than horizontal flight. The ability to escape in three dimensions by flying animals has been hypothesized to result in greater survival and eventually slower senescence than in animals only fleeing in two dimensions. In a comparative study of flight initiation distance in 69 species of birds when approached by a human, I found that the amount of variance explained by flight initiation distance was more than four times as large for the horizontal than the vertical component of perch height when taking flight. The slope of the relationship between horizontal distance and flight initiation distance (horizontal slope) increased with increasing body mass across species, whereas the slope of the relationship between vertical distance and flight initiation distance (vertical slope) decreased with increasing body mass. Therefore, there was a negative relationship between horizontal and vertical slope, although this negative relationship was significantly less steep than expected for a perfect trade‐off. The horizontal slope decreased with increasing density of the habitat from grassland over shrub to forest, whereas that was not the case for the vertical slope. Adult survival rate increased and rate of senescence (longevity adjusted for survival rate, body mass and sampling effort) decreased with increasing vertical, but not with horizontal slope, consistent with the prediction that vertical escape indeed provides a means of reducing the impact of predation.     

Barnacle Settlement on Hydrogels

Settlement of cultured Balanus amphitrite cyprid larvae was tested on different non-solid hydrogel surfaces. Gels consisting of alginate (highly anionic), chitosan (highly cationic), polyvinyl alcohol substituted with light-sensitive stilbazolium groups (PVA-SbQ; very low cationic) and agarose (neutral) were applied in cell culture multi-well plates. Polystyrene served as a solid surface reference. Preliminary experiments were performed to determine whether any substances leaching out of the gels could inhibit barnacle settlement. Whilst leachate from the gels revealed no toxicity towards Artemia salina nauplius larvae, PVA-SbQ in solution at and above a concentration of 0.4 ppm inhibited B. amphitrite cyprid settlement. Gels were therefore washed to avoid such effects during further testing, and toxicity and settlement tests with B. amphitrite nauplii and cyprids, respectively, applied to verify that washing was effective. Settlement was tested directly on the different test materials, followed by a quality test of non-settled larvae. All gels inhibited barnacle settlement compared to the polystyrene controls. Gels consisting of 2.5% PVA-SbQ or 0.5% agarose showed promising antifouling properties. Although some settlement occurred on 2.5% PVA-SbQ gels, metamorphosis was clearly inhibited. Only 10% of the larvae had settled on 0.5% agarose gels after 8 d. Less than 40% settlement occurred on alginate gels, as well as on 2% chitosan gels. Quality testing showed that the majority of remaining non-settled larvae in all gel experiments were able to settle when offered a suitable solid substratum.     

A method for determination of fresh weight of aquatic organisms

A precise and rapid method is described for the determination of fresh weight of aquatic plants and animals. The determination of fresh weight is done gravimetrically with a spectrophotometric estimate of adherent water providing a correction for adherent water.     

Isolation and characterisation of dog uropathogenic Escherichia coli strains and their fimbriae

A number of Escherichia coli strains have been isolated from dogs with urinary tract infections. These strains have been characterised with respect to their O, K, H, and fimbrial antigens, colicin production, antibiotic resistance, plasmid content and their ability to haemagglutinate erythrocytes from various species. Crossed immunoelectrophoresis of fimbrial extracts, as well as the reaction of partly purified fimbriae of a number of these strains with monoclonal antibodies revealed homology or a strong crossereaction with an F12 fimbrial subunit protein of human uropathogenic E. coli strains. Unlike human F12 fimbriae producing strains, the dog isolates did agglutinate dog erythrocytes in the presence of D-mannose but not human erythrocytes, indicating that the adhesin carried by these strains is different from the adhesin on fimbriae of human uropathogenic E. coli. Similar indications were obtained from experiments with latex beads coated with the receptor for P-fimbriae. These beads were agglutinated by Escherichia coli strains from human urinary tract infections, but not by the dog isolates described here. Preliminary adhesion experiments of human and dog Escherichia coli to human bladder epithelial and canine kidney epithelial cells also showed differences in adhesion depending on the origin of the strain tested.     

The influence of extra-cellular matrix and stroma remodeling on the productivity of long-term human bone marrow cultures

The stromal cell layer is believed to play an important role in long-term human bone marrow cultures (LTHBMCs). At present, neither the role that the stromal cell extra-cellular matrix (ECM) plays in influencing stroma behavior is well understood nor are the effects of stroma aging. Rapid medium exchanged LTHBMCs were established on surfaces precoated with human natural fibronectin and type 1 rat tail collagen. Although initial adhesion of hematopoietic cells was improved by the presence of both ECMs, the overall progenitor and nonadherent cell productivity was not improved nor did the stroma grow to confluency faster. Thus, the ECMs used did not significantly influence the cell productivity of LTHBMCs. To examine the influence of stromal cell layer aging, conditioned medium was obtained from the first two weeks of LTHBMCs that was subsequently concentrated and used as a medium supplement in a second set of slowly exchanged LTHBMCs. The presence of the concentrated conditioned medium (conCM) enhanced the production of nonadherent cells three-fold compared with control over an eight week culture period. Control cultures that were exposed to conCM after 4 weeks in culture significantly improved their cell productivity during the latter 4 weeks of culture compared with control. The productivity of cultures exposed to conCM for 4 weeks dropped significantly when unsupplemented medium was used for the latter 4 weeks of culture. Interestingly, phytohemagglutin-stimulated leukocyte-conditioned medium stimulated LTHMBCs in a similar fashion, as did conditioned medium from early LTHBMCs. Taken together, these results strongly suggest that the stromal cell layer does produce important factors for active hematopoiesis during its growth to confluence.     

Environmental variation partitioned into separate heritable components

Trait variation is normally separated into genetic and environmental components, yet genetic factors also control the expression of environmental variation, encompassing plasticity across environmental gradients and within‐environment responses. We defined four components of environmental variation: plasticity across environments, variability in plasticity, variation within environments, and differences in within‐environment variation across environments. We assessed these components for cold tolerance across five rearing temperatures using the Drosophila melanogaster Genetic Reference Panel (DGRP). The four components were found to be heritable, and genetically correlated to different extents. By whole genome single marker regression, we detected multiple candidate genes controlling the four components and showed limited overlap in genes affecting them. Using the binary UAS‐GAL4 system, we functionally validated the effects of a subset of candidate genes affecting each of the four components of environmental variation and also confirmed the genetic and phenotypic correlations obtained from the DGRP in distinct genetic backgrounds. We delineate selection targets associated with environmental variation and the constraints acting upon them, providing a framework for evolutionary and applied studies on environmental sensitivity. Based on our results we suggest that the traditional quantitative genetic view of environmental variation and genotype‐by‐environment interactions needs revisiting.     

Membrane adsorption characteristics determine the kinetics of flow-through transductions

Retrovirus-mediated gene transfer is currently limited by random Brownian motion of the retrovirus. This limitation can be overcome by flowing the retrovirus solution through a porous membrane that supports the target cells, leading to a significant increase in the transduction efficiency. This procedure is termed "flow-through transduction." In this study, we characterized the effects of the fluid flowrate and the influence that membrane characteristics have on the flow-through transduction procedure. The transduction efficiencies increased with flowrate until a plateau was reached at average flow velocities exceeding 0.3 cm/h for flow times of 3 to 4 h, using a collagen-coated depth (COL) membrane. A correlation between the optimal time for maximal gene transfer using flow-through transductions and the optimal time for maximal virus activity on the membrane was found, suggesting that the membrane adsorption capacity for virus determined the amount of gene transfer that could occur.Membrane adsorption characteristics were further investigated using two different membrane types: a tracketched polyester screen (PE) membrane and the COL membrane. Flow-through transductions using the PE and COL membranes showed that a high level of gene transfer could be attained using the COL membrane while the PE membrane gave much lower transduction efficiencies. The addition of the polycation polybrene (PB) changed these results markedly, making transductions achieved on the PE membrane similar in number to those obtained on the COL membrane. Since PB is believed to influence the virus adsorption to PE membrane, these results further support the conclusion that the increase in gene transfer achieved by the flow-through transduction procedure is due to virus adsorption to the membrane. The flow-through transduction procedure thus leads to co-localization of the viral vector and the target cell that in turn leads to a high transduction efficiency. (c) 1996 John Wiley & Sons, Inc.