High fat diet-induced maternal obesity in mice impairs peripartum maternal behaviour.

Obesity during pregnancy represents a significant health issue and can lead to increased complications during pregnancy and impairments with breastfeeding, along with long-term negative health consequences for both mother and offspring. In rodent models, diet-induced obesity (DIO) during pregnancy leads to poor outcomes for offspring. Using a DIO mouse model, consisting of feeding mice a high fat diet for 8 weeks before mating, we recapitulate the effect of high pup mortality within the first 3 days postpartum. To examine the activity of the dam around the time of birth, late pregnant control and DIO dams were recorded in their home cages and the behaviour of the dam immediately before and after birth was analysed. Prior to giving birth, DIO dams spent less time engaging in nesting behaviour, while after birth, DIO dams spent less time in the nest with their pups compared to control dams, indicating reduced pup-engagement in the early postpartum period. We have previously reported that lactogenic hormone action, mediated by the prolactin receptor, in the medial preoptic area of the hypothalamus (MPOA) is critical for the onset of normal postpartum maternal behaviour. We hypothesized that DIO dams may have lower lactogenic hormone activity during late pregnancy, which would contribute to impaired onset of normal postpartum maternal behaviour. Day 16 lactogenic activity, transport of prolactin into the brain, and plasma prolactin concentrations around birth were all similar in control and DIO dams. Moreover, endogenous pSTAT5, a marker of prolactin receptor activity, in the MPOA was unaffected by DIO. Overall, these data indicate that lactogenic activity in late pregnancy of DIO dams is not different to controls and is unlikely to play a major role in impaired onset of normal postpartum maternal behaviour.

A role for fibroblast-derived SASP factors in the activation of pyroptotic cell death in mammary epithelial cells.

In normal tissue homeostasis, bidirectional communication between different cell types can shape numerous biological outcomes. Many studies have documented instances of reciprocal communication between fibroblasts and cancer cells that functionally change cancer cell behavior. However, less is known about how these heterotypic interactions shape epithelial cell function in the absence of oncogenic transformation. Furthermore, fibroblasts are prone to undergo senescence, which is typified by an irreversible cell cycle arrest. Senescent fibroblasts are also known to secrete various cytokines into the extracellular space; a phenomenon that is termed the senescence-associated secretory phenotype (SASP). While the role of fibroblast-derived SASP factors on cancer cells has been well studied, the impact of these factors on normal epithelial cells remains poorly understood. We discovered that treatment of normal mammary epithelial cells with conditioned media from senescent fibroblasts (SASP CM) results in a caspase-dependent cell death. This capacity of SASP CM to cause cell death is maintained across multiple senescence-inducing stimuli. However, the activation of oncogenic signaling in mammary epithelial cells mitigates the ability of SASP CM to induce cell death. Despite the reliance of this cell death on caspase activation, we discovered that SASP CM does not cause cell death by the extrinsic or intrinsic apoptotic pathway. Instead, these cells die by an NLRP3, caspase-1, and gasdermin D-dependent induction of pyroptosis. Taken together, our findings reveal that senescent fibroblasts can cause pyroptosis in neighboring mammary epithelial cells, which has implications for therapeutic strategies that perturb the behavior of senescent cells.

Evaluating changes to home bowel cancer screening kits: an end-user perspective study.

PURPOSE: Many people do not participate in mail-out bowel cancer screening programs due to difficulties using the screening kit. The current study investigated the ways the screening kit could be modified to improve usability. METHODS: 1,109 people evaluated 15 different screening kit modifications. Participants reported on how these kit modifications would affect their screening barriers, their future screening intentions, and how much they would recommend that the modification is made to the current screening kit used the program. All responses were given via an online survey conducted between April and December of 2021. RESULTS: Seventeen percent of previous NBCSP non-participators indicated that a one-sample test would increase their intention to participate. Recommendation ratings demonstrated higher levels of support for modifications that included providing a barcode naming label (M = 9.06, 95% CI [8.81, 9.31]), having a larger diameter opening of the collection tube (M = 8.42, 95% CI [8.10, 8.74]), and highlighting the expiry date on the kit packaging (M = 8.59, 95% CI [8.29, 8.89]). There were lower levels of support for modifications that reduced the size of the packaging the kit is sent in (M = 6.47, 95% CI [6.09, 6.85]), removed branding from kit packaging (M = 5.98, 95% CI [5.57, 6.39]), and removed the information booklet that comes with the screening kit (M = 5.25, 95% CI [4.78, 5.72]). CONCLUSION: These findings highlight multiple ways in which bowel cancer screening kits can be changed to increase usability for invitees of national bowel cancer screening programs. Findings have implications for all screening programs that use immunochemical-based bowel cancer screening kits.

A role for fibroblast-derived SASP factors in the activation of pyroptotic cell death in mammary epithelial cells.

In normal tissue homeostasis, bidirectional communication between different cell types can shape numerous biological outcomes. Many studies have documented instances of reciprocal communication between fibroblasts and cancer cells that functionally change cancer cell behavior. However, less is known about how these heterotypic interactions shape epithelial cell function in the absence of oncogenic transformation. Furthermore, fibroblasts are prone to undergo senescence, which is typified by an irreversible cell cycle arrest. Senescent fibroblasts are also known to secrete various cytokines into the extracellular space; a phenomenon that is termed the senescence-associated secretory phenotype (SASP). While the role of fibroblast derived SASP factors on cancer cells has been well studied, the impact of these factors on normal epithelial cells remains poorly understood. We discovered that treatment of normal mammary epithelial cells with conditioned media (CM) from senescent fibroblasts (SASP CM) results in a caspase-dependent cell death. This capacity of SASP CM to cause cell death is maintained across multiple senescence-inducing stimuli. However, the activation of oncogenic signaling in mammary epithelial cells mitigates the ability of SASP CM to induce cell death. Despite the reliance of this cell death on caspase activation, we discovered that SASP CM does not cause cell death by the extrinsic or intrinsic apoptotic pathway. Instead, these cells die by an NLRP3, caspase-1, and gasdermin D (GSDMD)-dependent induction of pyroptosis. Taken together, our findings reveal that senescent fibroblasts can cause pyroptosis in neighboring mammary epithelial cells, which has implications for therapeutic strategies that perturb the behavior of senescent cells.

Oncogenic signaling inhibits c-FLIPL expression and its non-apoptotic function during ECM-detachment.

Inhibition of programmed cell death pathways is frequently observed in cancer cells where it functions to facilitate tumor progression. However, some proteins involved in the regulation of cell death function dichotomously to both promote and inhibit cell death depending on the cellular context. As such, understanding how cell death proteins are regulated in a context-dependent fashion in cancer cells is of utmost importance. We have uncovered evidence that cellular FLICE-like Inhibitory Protein (c-FLIP), a well-known anti-apoptotic protein, is often downregulated in tumor tissue when compared to adjacent normal tissue. These data argue that c-FLIP may have activity distinct from its canonical role in antagonizing cell death. Interestingly, we have discovered that detachment from extracellular matrix (ECM) serves as a signal to elevate c-FLIP transcription and that oncogenic signaling blocks ECM-detachment-induced c-FLIP elevation. In addition, our data reveal that downregulation of c-FLIP promotes luminal filling in mammary acini and that c-FLIP overexpression in cancer cells inhibits colony formation in cells exposed to ECM-detachment. Taken together, our study reveals an unexpected, non-apoptotic role for c-FLIP during ECM-detachment and raises the possibility that c-FLIP may have context-dependent roles during tumorigenesis.

The Interoception Sensory Questionnaire (ISQ): A Scale to Measure Interoceptive Challenges in Adults.

Increasing attention is being paid to how adults on the autism spectrum perceive and interpret the interoceptive sense. This 20-item Interoception Sensory Questionnaire represents a single factor scale that can be interpreted as representing confusion about interoceptive bodily states unless these states are extreme (Alexisomia), and has been designed to discriminate across populations (total sample 511 participants). Findings showed that 74% of adults with autism reported interoceptive confusion. Another finding of the study was that as autistic traits increased, interoceptive confusion increased, with adults with diagnosed autism scoring highest on the construct. Implications for physiological self-regulation as well as physical health outcomes are discussed, as well as recommendations for future research.

Modal noise in an integrated photonic lantern fed diffraction-limited spectrograph.

In an attempt to develop a streamlined astrophotonic instrument, we demonstrate the realization of an all-photonic device capable of both multimode to single mode conversion and spectral dispersion on an 8-m class telescope with efficient coupling. The device was a monolithic photonic spectrograph which combined an integrated photonic lantern and an efficient arrayed waveguide grating device. During on-sky testing, we discovered a previously unreported type of noise that made spectral extraction and calibration extremely difficult. The source of the noise was traced to a wavelength-dependent loss mechanism between the feed fiber's multimode near-field pattern and the modal acceptance profile of the integrated photonic lantern. Extensive modeling of the photonic components replicates the wavelength-dependent loss, and demonstrates an identical effect on the final spectral output. We outline that this could be mitigated by directly injecting into the integrated photonic lantern.

Enhancing antimicrobial stewardship by strengthening the veterinary drug regulatory framework.

Antimicrobial resistance is a major and growing public health threat. Recently, Health Canada introduced multiple regulatory changes to strengthen the oversight of antimicrobial drugs for veterinary use. These changes aim specifically at increasing control over importation of veterinary drugs and active pharmaceutical ingredients, mandatory reporting of antimicrobial sales data from manufacturers, importers and compounders and facilitating access to low risk veterinary health products. Additional policy changes under existing authorities are also being made to enhance veterinary supervision of antimicrobial use and to remove production claims for food animals from labels of medically important antimicrobial drugs. These important interlinked initiatives are aimed towards enhancing antimicrobial stewardship in Canada to preserve the effectiveness of existing antimicrobials and to protect the health of Canadians.

The expanding fireball of Nova Delphini 2013.

A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common-envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes as it expands. We detect an ellipticity in the light distribution, suggesting a prolate or bipolar structure that develops as early as the second day. Combining the angular expansion rate with radial velocity measurements, we derive a geometric distance to the nova of 4.54 ± 0.59 kiloparsecs from the Sun.

HD 181068: a red giant in a triply eclipsing compact hierarchical triple system.

Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by ground-based spectroscopy and interferometry, which show it to be a hierarchical triple with two types of mutual eclipses. The primary is a red giant that is in a 45-day orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows evidence for tidally induced oscillations that are driven by the orbital motion of the close pair. HD 181068 is an ideal target for studies of dynamical evolution and testing tidal friction theories in hierarchical triple systems.

Distinct receptors underlie glutamatergic signalling in inspiratory rhythm-generating networks and motor output pathways in neonatal rat.

Despite the enormous diversity of glutamate (Glu) receptors and advances in understanding recombinant receptors, native Glu receptors underlying functionally identified inputs in active systems are poorly defined in comparison. In the present study we use UBP-302, which antagonizes GluR5 subunit-containing kainate (KA) receptors at < or = 10 microm, but other KA and AMPA receptors at > or = 100 microm, and rhythmically active in vitro preparations of neonatal rat to explore the contribution of non-NMDA receptor signalling in rhythm-generating and motor output compartments of the inspiratory network. At 10 microm, UBP-302 had no effect on inspiratory burst frequency or amplitude. At 100 microm, burst amplitude recorded from XII, C1 and C4 nerve roots was significantly reduced, but frequency was unaffected. The lack of a frequency effect was confirmed when local application of UBP-302 (100 microm) into the pre-Bötzinger complex (preBötC) did not affect frequency but substance P evoked a 2-fold increase. A UBP-302-sensitive (10 microm), ATPA-evoked frequency increase, however, established that preBötC networks are sensitive to GluR5 activation. Whole-cell recordings demonstrated that XII motoneurons also express functional GluR5-containing KA receptors that do not contribute to inspiratory drive, and confirmed the dose dependence of UBP-302 actions on KA and AMPA receptors. Our data provide the first evidence that the non-NMDA (most probably AMPA) receptors mediating glutamatergic transmission within preBötC inspiratory rhythm-generating networks are pharmacologically distinct from those transmitting drive to inspiratory motoneurons. This differential expression may ultimately be exploited pharmacologically to separately counteract depression of central respiratory rhythmogenesis or manipulate the drive to motoneurons controlling airway and pump musculature.

Imaging the surface of Altair.

Spatially resolving the surfaces of nearby stars promises to advance our knowledge of stellar physics. Using optical long-baseline interferometry, we constructed a near-infrared image of the rapidly rotating hot star Altair with a resolution of <1 milliarcsecond. The image clearly reveals the strong effect of gravity darkening on the highly distorted stellar photosphere. Standard models for a uniformly rotating star cannot explain our findings, which appear to result from differential rotation, alternative gravity-darkening laws, or both.

A randomised controlled trial of the use of a tourniquet to reduce blood loss during transtibial amputation for peripheral arterial disease.

OBJECTIVES: To examine the effects of an exsanguination tourniquet on blood loss during transtibial amputation in patients with peripheral arterial disease (PAD). DESIGN: Prospective randomised blinded controlled trial. MATERIALS AND METHODS: Sixty-four patients undergoing transtibial amputation for non-reconstructible PAD were randomised to either tourniquet or no tourniquet (control). Blood loss (primary outcome), fall in haemoglobin, transfusion requirements, wound healing, breakdown and revision (secondary outcomes) were also recorded. RESULTS: Twenty-five patients in the tourniquet and 29 in the control group conformed to the trial protocol and completed the follow up. Intra-operative blood loss (median and IQR) was significantly greater in the control group compared to the tourniquet group (550 ml (255-1050) vs 255 ml (150-572.5), respectively, p=0.014, Mann-Whitney). There was a significantly greater drop in haemoglobin concentration (median and IQR) in the control compared to the tourniquet group (1.8 g/dl (0-1.2) vs 1.0 g/dl (0.6-2.4), p=0.035, t-test). Transfusion requirements were lower in the tourniquet group (p=0.05, Mann-Whitney). The rate of wound healing, breakdown and revision were similar in the tourniquet and control groups, respectively (59 vs 57%, 0 vs 9%, 14 vs 9%, p=NS). CONCLUSIONS: The use of a tourniquet during transtibial amputation for severe PAD reduces blood loss and need for blood transfusion.

The response of general practitioners to the threat of violence in their practices: results from a qualitative study.

BACKGROUND: Violence directed towards GPs has been recognized as a significant problem in the UK. In Australian urban general practice, no study has previously examined this topic. OBJECTIVE: The objective of this study was to investigate the responses of Australian urban GPs to experiences of violence and to perceptions of risk of violence. DESIGN: A qualitative study of data collected from two sources-focus group discussions and qualitative questionnaire responses. Focus group discussions were audiotaped and transcribed. Questionnaires offered the opportunity for respondents to make qualitative comments. The focus group transcripts and qualitative questionnaire responses were coded independently by members of the research team and subjected to thematic analysis. SETTING: Three urban Divisions of General Practice in New South Wales, Australia. SUBJECTS: Focus groups were conducted with male and female GPs comprising a range of ages, socio-economic practice catchments and practice structures. Questionnaires were distributed to all GPs in the three divisions. RESULTS: The GPs in this study perceived themselves as being at significant risk of occupational violence. Despite responses to violence being largely ad hoc and uncoordinated, a coherent schema of GPs' responses to the threat of violence is apparent in the data. This has been characterized as encompassing primary, secondary and tertiary responses, and reflects a continuum of proactive to reactive responses. CONCLUSION: The findings will have implications for further research and for policy in the area.

Identifying psychosocial problems among youth: factors associated with youth agreement on a positive parent-completed PSC-17.

BACKGROUND: The choice of informant is a critical piece in the identification of psychosocial problems in youth. While many behavioural measures have been adapted to include information from multiple sources, in the case of parents and youth, poor agreement has been found. Our study purpose was to identify youth and parent factors associated with whether the youth agrees with a positive parent-completed screen of youth psychosocial problems. METHODS: Parents of youth aged 10-15 years who were seen for a medical visit at eight clinics completed the 17-item Pediatric Symptom Checklist (PSC-17). Youth scoring positive on the screen and their parents/guardians were interviewed by telephone after the visit (n = 145). We conducted bivariate and multivariate analyses to identify parent characteristics and child factors associated with whether the youth agrees with the positive parent-completed screen. RESULTS: Fifty per cent of youth participants agreed with their parent on a positive parent-completed PSC-17 based on their completion of the Y-PSC-17 as a self-report measure. Youth who reported a positive Y-PSC-17 in agreement with their parent were twice as likely to meet diagnostic cut-offs on sub-scales of anxiety/depression and aggression on the Child Behaviour Checklist (P < 0.01 and P < 0.05 respectively), reported lower parent-child connectedness (P < 0.01) and their parents reported more anger/frustration (P < 0.05) than youth who disagreed with the positive parent-completed screen. Most of these associations remained significant when controlling for the other factors and demographic characteristics in multivariate analysis. CONCLUSIONS: Findings indicate that when the youth agrees with a positive parent-completed PSC-17, there is higher parent frustration, lower parent-child connectedness, and the youth is more likely to have a diagnosis of an emotional or behavioural disorder. Thus, when possible, the use of both parent and youth as informants provides necessary information in formulating a comprehensive treatment strategy to address the psychosocial needs of youth.

Mapping the effects of the selective dopamine D2/D3 receptor agonist quinelorane using pharmacological magnetic resonance imaging.

Dopamine agonists with a high affinity for D2 and D3 receptors have a biphasic effect on rodent locomotion, inducing hypolocomotion at low doses and hyperlocomotion at higher doses. Controversy surrounds the role of the D3 receptor in mediating the hypolocomotor response to low agonist doses. This study examines patterns of neuronal activation induced by varying doses of the D2/D3 receptor agonist quinelorane using blood oxygen level dependent (BOLD) pharmacological magnetic resonance imaging (phMRI), and compares them with corresponding behavioural responses. Quinelorane (3 microg/kg) induced hypolocomotion in rats naive to the testing environment, and in phMRI experiments increased neuronal activity within the anterior olfactory nuclei, nucleus accumbens and islets of Calleja, regions containing a high density of D3 receptors. A 30 microg/kg dose of quinelorane resulted in biphasic locomotor effects, with initial hypolocomotion followed by sustained hyperlocomotion. phMRI indicated that this higher dose increased cerebral activity within limbic and olfactory regions, as did the lower drug dose, but induced additional activation in the caudate-putamen and globus pallidus, areas dense in D2 receptors but containing few D3 receptors. The more restricted pattern of activation at low agonist doses and close temporal relationship between behavioural and BOLD signal responses to quinelorane suggest that those nuclei most dense in D3 receptors play a key role in mediating the hypolocomotor effects of quinelorane. However, the presence of D3 receptors in activated brain regions may be coincidental, and further studies are required to show definitively which class of receptors mediates agonist-induced hypolocomotion. In contrast, the activation of D2 receptors within the striatum appears necessary for quinelorane-induced hyperlocomotion.

Results from the prospective registry of endovascular treatment of abdominal aortic aneurysms (RETA): mid term results to five years.

OBJECTIVES: To assess the mid-term outcomes up to 5 years following endovascular repair of abdominal aortic aneurysms (EVAR), following its initial introduction into practice in the UK. DESIGN: A prospective voluntary Registry of Endovascular Treatment of Aneurysms (RETA) collected demographic and risk factor data, short term (30 day) outcomes and follow up outcomes up to 5 years from the 41 centres that initially undertook EVAR in the UK. RESULTS: Short term outcomes (30 days): 90.4% of aneurysms were successfully excluded, 6.1% had persistent endoleaks and 5.8% of patients had died. Follow up was obtained from 30 days up to 5 years (mean 3.1 years). Returns rates for requested follow up data were 87% at 1 year and 77, 65, 52 and 51% at 2, 3, 4 and 5 years, respectively. Ninety percent of deaths at follow up were unrelated to the stent-graft or aneurysm. Persistent proximal type I endoleak was associated with significant mortality both from attempted open repair or from rupture if untreated. Other endoleaks were more benign. Complications related to the aneurysm or device occurred at an average rate of 15% per annum. The most common complications were secondary endoleaks or graft migration. Endovascular treatment was preferred if treatment was necessary for graft complications. The cumulative freedom from secondary procedure (Kaplan-Meier) were 87, 77, 70, 65 and 62% at 1, 2, 3, 4 and 5 years of follow up, respectively. CONCLUSIONS: Registry data provides useful information to guide the design of more formal trials. Collecting follow up from voluntarily submitted data is difficult. The registry data remains well ahead of the trial data, but indicate that long term follow up is required in these trials, because of the high rate of complications seen at follow up.

After hours care--a qualitative study of GPs' perceptions of risk of violence and effect on service provision.

BACKGROUND: Workplace violence in general practice has been found to be an important problem in the United Kingdom. No research has been undertaken in this area in Australian urban practice. METHOD: Four focus groups involved 18 urban general practitioners and over 9 hours of taped responses were transcribed. The transcripts were coded and subjected to thematic analysis. RESULTS: General practitioners expressed a wide range of risks relating to the provision of after hours care. This makes them apprehensive about participating in it. Those who had experienced violence, or perceived its risk, had limited their participation in after hours care; sometimes completely. DISCUSSION: Structures may be needed to support provision of after hours general practice services.

P2X7-like receptor subunits enhance excitatory synaptic transmission at central synapses by presynaptic mechanisms.

Recent studies demonstrate that P2X7 receptor subunits (P2X7RS) are present at central and peripheral synapses and suggest that P2X7RS can regulate transmitter release. In brainstem slices from 15 to 26 day old pentobarbitone-anesthetized mice, we examined the effect of P2X7RS activation on excitatory postsynaptic currents (EPSCs) recorded from hypoglossal motoneurons using whole-cell patch clamp techniques. After blockade of most P2X receptors with suramin (which is inactive at P2X7RS) and of adenosine receptors with 8-phenyltheophylline (8PT), bath application of the P2X receptor agonist 3'-0-(4-benzoyl)ATP (BzATP) elicited a 40.5+/-16.0% (mean+/-S.E.M., n = 8, P = 0.039) increase in evoked EPSC amplitude and significantly reduced paired pulse facilitation of evoked EPSCs. This response to BzATP (with suramin and 8PT present) was completely blocked by prior application of Brilliant Blue G (200 nM or 2 microM), a P2X7RS antagonist. In contrast, BzATP application with suramin and 8PT present did not alter miniature EPSC frequency or amplitude when action potentials were blocked with tetrodotoxin. These electrophysiological results suggest that P2X7RS activation increases central excitatory transmitter release via presynaptic mechanisms, confirming previous indirect measures of enhanced transmitter release. We suggest that possible presynaptic mechanisms underlying enhancement of evoked transmitter release by P2X7RS activation are modulation of action potential width or an increase in presynaptic terminal excitability, due to subthreshold membrane depolarization which increases the number of terminals releasing transmitter in response to stimulation.

To know that we know what we know: perceived knowledge and adolescent sexual risk behavior.

STUDY OBJECTIVE: To examine the relationship between perceived knowledge about sex and adolescent sexual behaviors. DESIGN: Secondary analysis of the 2001 Minnesota Student Survey. Bivariate and multivariate relationships between perceived knowledge about sex and sexual behaviors were examined. SETTING: Minnesota. PARTICIPANTS: 83,481 9(th) and 12(th) grade public school students. MAIN OUTCOME MEASURES: Students' report of sexual experience and sexual behaviors. RESULTS: Students with low perceived knowledge were less likely to be sexually experienced (OR=0.22, CI=0.17-0.29, females, OR=0.70, CI=0.59-0.82, males, P=0.00). Among sexually active students, those with low perceived knowledge also had significantly higher odds of engaging in risky sexual behaviors. Sexually experienced females with low perceived knowledge were more likely to report not talking with their partners about STIs (OR=1.83, CI=1.1-3.16, P=0.02), a history of pregnancy (OR=2.87, CI=1.59-5.18, P=0.00), and had higher numbers of male (P=0.03) and female (P=0.00) sexual partners. Sexually experienced males with low perceived knowledge were more likely to report not talking with their partners about pregnancy (OR=1.43, CI=1.11-1.84, P=0.01), pregnancy involvement (OR=2.22, CI=1.65-2.95, P=0.00), inconsistent use of birth control (OR=1.30, CI= 1.01-1.68, P=0.04), inconsistent use of condoms (OR=1.79, CI=1.38-2.32, P=0.00), not using a condom at last intercourse (OR=1.58, CI=1.22-2.04, P=0.00), and had a higher numbers of male (P=0.00) and female (P=0.00) sexual partners. CONCLUSIONS: Perceived knowledge may be a salient antecedent of adolescent sexual risk behavior. Health care providers and programs should incorporate the construct of perceived knowledge into their assessments of and interventions targeted at adolescents.