Bacteroides fragilis toxin expression enables lamina propria niche acquisition in the developing mouse gut.

Bacterial toxins are well-studied virulence factors; however, recent studies have revealed their importance in bacterial niche adaptation. Enterotoxigenic Bacteroides fragilis (ETBF) expresses B. fragilis toxin (BFT) that we hypothesized may contribute to both colonic epithelial injury and niche acquisition. We developed a vertical transmission model for ETBF in mice that showed that BFT enabled ETBF to access a lamina propria (LP) niche during colonic microbiome development that was inaccessible to non-toxigenic B. fragilis. LP entry by ETBF required BFT metalloprotease activity, and showed temporal restriction to the pre-weaning period, dependent on goblet-cell-associated passages. In situ single-cell analysis showed bft expression at the apical epithelial surface and within the LP. BFT expression increased goblet cell number and goblet-cell-associated passage formation. These findings define a paradigm by which bacterial toxin expression specifies developmental niche acquisition, suggesting that a selective advantage conferred by a toxin may impact long-term host health.

Erotic Pleasure and Pleasure-Seeking Associated with Implicit and Explicit Sexual Motives.

Two studies examined the proposal that implicit and explicit sexual motives are associated with the experience of pleasure in sexual situations, as well as with seeking out sexual pleasure. In Study 1, implicit and explicit motive scores of 145 heterosexually identified women and 152 heterosexually identified men were demonstrated to be independently associated with the experience of pleasure in response to videos of female-male sexual behavior, more consistently so for women than men. The implicit and explicit motive scales were also associated with the frequency of viewing erotic materials in daily life. The experience of pleasure within sexual relationships was additionally shown to be associated with sexual motives, although primarily implicit motives. In Study 2 involving 139 women and 65 men, implicit motive scales were associated with ratings of interest in a potential romantic partner. The results support the conceptualization of the two instruments as measures of sexual motivation. The difference between implicit versus explicit measures in the pattern of correlations involving acquainted versus non-acquainted individuals is consistent with research on ideal partner preference.

Changes in the material properties of the shell during simulated aquatic hibernation in the anoxia-tolerant painted turtle.

Western painted turtles (Chrysemys picta bellii) tolerate anoxic submergence longer than any other tetrapod, surviving more than 170 days at 3°C. This ability is due, in part, to the shell and skeleton simultaneously releasing calcium and magnesium carbonates, and sequestering lactate and H+ to prevent lethal decreases in body fluid pH. We evaluated the effects of anoxic submergence at 3°C on various material properties of painted turtle bone after 60, 130 and 167-170 days, and compared them with those of normoxic turtles held at the same temperature for the same time periods. To assess changes in the mechanical properties, beams (4×25 mm) were milled from the plastron and broken in a three-point flexural test. Bone mineral density, CO2 concentration (a measure of total bone HCO3-/CO32-) and elemental composition were measured using microcomputed tomography, HCO3-/CO32- titration and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Tissue mineral density of the sampled bone beams was not significantly altered by 167-170 days of aquatic overwintering in anoxic or normoxic water, but bone CO2 and Mg were depleted in anoxic compared with normoxic turtles. At this time point, the plastron beams from anoxic turtles yielded at stresses that were significantly smaller and strains that were significantly greater than the plastron beams of normoxic turtles. When data from anoxic and normoxic turtles were pooled, plastron beams had a diminished elastic modulus after 167-170 days compared with those of control turtles sampled on day 1, indicating an effect of prolonged housing of the turtles in 3°C water without access to basking sites. There were no changes in the mechanical properties of the plastron beams at any of the earlier time points in either group. We conclude that anoxic hibernation can weaken the painted turtle's plastron, but likely only after durations that exceed what it might naturally experience. The duration of aquatic overwintering, regardless of oxygenation state, is likely to be an important factor determining the mechanical properties of the turtle shell during spring emergence.

Transcriptomic Responses of the Heart and Brain to Anoxia in the Western Painted Turtle.

Painted turtles are the most anoxia-tolerant tetrapods known, capable of surviving without oxygen for more than four months at 3°C and 30 hours at 20°C. To investigate the transcriptomic basis of this ability, we used RNA-seq to quantify mRNA expression in the painted turtle ventricle and telencephalon after 24 hours of anoxia at 19°C. Reads were obtained from 22,174 different genes, 13,236 of which were compared statistically between treatments for each tissue. Total tissue RNA contents decreased by 16% in telencephalon and 53% in ventricle. The telencephalon and ventricle showed ≥ 2x expression (increased expression) in 19 and 23 genes, respectively, while only four genes in ventricle showed ≤ 0.5x changes (decreased expression). When treatment effects were compared between anoxic and normoxic conditions in the two tissue types, 31 genes were increased (≥ 2x change) and 2 were decreased (≤ 0.5x change). Most of the effected genes were immediate early genes and transcription factors that regulate cellular growth and development; changes that would seem to promote transcriptional, translational, and metabolic arrest. No genes related to ion channels, synaptic transmission, cardiac contractility or excitation-contraction coupling changed. The generalized expression pattern in telencephalon and across tissues, but not in ventricle, correlated with the predicted metabolic cost of transcription, with the shortest genes and those with the fewest exons showing the largest increases in expression.

Nonresponse bias in a mail survey of physicians.

With the increased pressure on survey researchers to achieve high response rates, it is critical to explore issues related to nonresponse. In this study, the authors examined the effects of nonresponse bias in a mail survey of physicians (N = 3,400). Because slightly more than one half of the sample did not respond to the survey, there was potential for bias if nonresponders differed significantly from responders with respect to key demographic and practice variables. They analyzed response status and timing of response with respect to five variables: gender, region, specialty, urbanicity, and survey length. The potential consequences of nonresponse bias on the survey estimates were then analyzed. Men were more likely to respond, as were physicians receiving a shorter questionnaire. Repeated follow-up attempts reduced gender response bias because male physicians were more likely to be early responders. Overall, higher response rates were not associated with lower response bias.

Survey response inducements for registered nurses.

The past 20 years have seen an overall decline in survey response rates and an even more pronounced decline in samples of health care professionals. The authors tested the use of a "thank you" or "reminder" postcard as a method by which to stem the tide of declining response rates. The authors conducted a mail and telephone survey of 49,605 registered nurses for the 2000 National Sample Survey of Registered Nurses and sent an extra mailing to a random subsample (n = 4,968). They then compared response rates for both groups. Contrary to prior research, this study found that reminder postcards did not improve response rates or rates of return. There may be several reasons for this finding, including the general familiarity with, and high saliency of, this research project for the nursing community. These results suggest that even widely accepted best practices for survey methods deserve scrutiny when applied to special subpopulations.

Gender, relationship stage, and sexual behavior: the importance of partner emotional investment within specific situations.

This study examined the relationship of type of sexually instigating situation (partner behavior conveying emotional investment or not), relationship stage, and gender to self-reported likelihood of engaging in sexual behavior. Participants (200 female and 122 male college students) read scenarios describing partner behavior in eight hypothetical sexual situations. Five of the sexual situations were proposed to explicitly communicate a sense of emotional investment in the relationship, and three other scenarios were conceived as not explicitly conveying emotional investment. Emotional investment situations were hypothesized to influence likelihood ratings as a function of imagined relationship stage (dating or in a serious relationship), manipulated across participants. Situations not conveying investment were hypothesized to influence ratings as a function of both relationship stage and gender. In large part, hypotheses were confirmed. The few exceptions were consistent with other gender-role considerations related to trust and power.

Challenged to care: informal caregivers in a changing health system.

This report is from a 1998 national survey of 1,002 informal caregivers. Each year 23 percent of Americans provide unpaid assistance to ill, disabled, or elderly persons. Most caregivers (71 percent) do not live with care recipients. Primary caregivers provide more care of all types. Nonprimary caregivers also provide substantial care and services. Caregivers perform complex medical tasks, including medication administration, and errors can result. Few receive assistance from paid professionals or aides because of quality or financial concerns. In many areas, support and instruction could lighten caregivers' burdens and help to ensure high-quality care at home.