Premenopausal women express reduced blood pressure and risk of cardiovascular disease relative to age-matched men. This purportedly relates to elevated estrogen levels increasing nitric oxide synthase (NOS) activity and NO-mediated vasorelaxation. We tested the hypotheses that female rat skeletal muscle would: 1) evince a higher O delivery-to-utilization ratio (Q̇o/V̇o) during contractions; and 2) express greater modulation of Q̇o/V̇o with changes to NO bioavailability compared with male rats. The spinotrapezius muscle of Sprague-Dawley rats (females = 8, males = 8) was surgically exposed and electrically-stimulated (180 s, 1 Hz, 6 V). OxyphorG4 was injected into the muscle and phosphorescence quenching employed to determine the temporal profile of interstitial Po (Po, determined by Q̇o/V̇o). This was performed under three conditions: control (CON), 300 µM sodium nitroprusside (SNP; NO donor), and 1.5 mM N-nitro-l-arginine methyl ester (l-NAME; NOS blockade) superfusion. No sex differences were found for the Po kinetics parameters in CON or l-NAME ( P > 0.05), but females elicited a lower baseline following SNP (males 42 ± 3 vs. females 36 ± 2 mmHg, P < 0.05). Females had a lower ΔPo during contractions following SNP (males 22 ± 3 vs. females 17 ± 2 mmHg, P < 0.05), but there were no sex differences for the temporal response to contractions ( P > 0.05). The total NO effect (SNP minus l-NAME) on Po was not different between sexes. However, the spread across both conditions was shifted to a lower absolute range for females (reduced SNP baseline and greater reduction following l-NAME). These data support that females have a greater reliance on basal NO bioavailability and males have a greater responsiveness to exogenous NO and less responsiveness to reduced endogenous NO. NEW & NOTEWORTHY Interstitial Po (Po; determined by O delivery-to-utilization matching) plays an important role for O flux into skeletal muscle. We show that both sexes regulate Po at similar levels at rest and during skeletal muscle contractions. However, modulating NO bioavailability exposes sex differences in this regulation with females potentially having a greater reliance on basal NO bioavailability and males having a greater responsiveness to exogenous NO and less responsiveness to reduced endogenous NO.

Objective The aim of this study was to investigate the prevalence, breed predisposition and fracture conformation of humeral condylar fractures (HCF) over a 10-year period. Results were compared with published studies emanating from the United Kingdom exploring effect of breed on HCF. Methods Data for all canine admissions to the Veterinary Teaching Hospital at Kansas State University were extracted for the period January 2010 to October 2020. Humeral fractures were recorded and further subclassified as medial, lateral and ‘T’/‘Y’ condylar fractures. The associations between HCF and subtypes with breed were assessed using univariate logistic regression with a comparison group. Multivariable logistic regression was used to evaluate the effect of breed while accounting for dog age, sex and neuter status. Results Of the 44,952 canine patients seen during the study period, period prevalence (95% confidence interval [CI] for HCF was 0.26% [0.22, 0.31]). After adjustment for age and neuter status, French Bulldogs were 49 times more likely to be diagnosed with a HCF compared with the comparison breed group (odds ratio [OR], 49.0; 95% CI, 26.9–89.3). After adjustment for age and neuter status, Cocker Spaniels (OR, 42.8; 95% CI, 16.8–108.6), Boston Terriers (OR, 22.9; 95% CI, 11.0–47.9) and Brittany Spaniels (OR, 21.5; 95% CI, 7.3–63.1) had the next highest increase in HCF compared with the comparison group. Conclusion Based on a study population from the United States, French Bulldogs were 49 times more likely to be diagnosed with a HCF compared with the comparison breed group.

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