Noninvasive Monitoring of Blood Pressure and Heart Rate during Estrous Cycle Phases in Normotensive Wistar-Kyoto and Spontaneously Hypertensive Female Rats

Since 2015, the National Institutes of Health has called for its funded preclinical research to include both male and female subjects. However, much of the basic animal research that has studied heart rate and blood pressure in the past has used male rats. Male rats have been preferred for these studies to avoid the possible complicating effects of the female estrous cycle. The aim of the current study was to determine whether blood pressure and heart rates vary as a function of the estrous cycle phase of young normotensive Wistar-Kyoto (WKY) and Spontaneously Hypertensive (SHR) female rats. Blood pressure and heart rate were measured at the same time of day throughout the estrous cycle by using a noninvasive tail cuff sphygmomano- metric technique. As expected, 16-wk-old female SHR rats had higher blood pressure and heart rates than did age-matched female WKY rats. However, no significant differences in mean, systolic, or diastolic arterial blood pressure or heart rate were detected across the different stages of the estrous cycle in either strain of female rats. Consistent with previous reports, heart rates were higher and showed less variation in the hypertensive SHR female rats as compared with the normotensive WKY female rats. These results indicate that studies measuring blood pressure and heart rate can include young female SHR and WKY rats with no effect of estrous cycle stage.

The development and application of a high-sensitivity immunoassay for cardiac myosin-binding protein C

Cardiac troponins (cTns) are released and cleared slowly after myocardial injury. Cardiac myosin-binding protein C (cMyC) is a similar cardiac-restricted protein that has more rapid release and clearance kinetics. Direct comparisons are hampered by the lack of an assay for cMyC that matches the sensitivity of the contemporary assays for cTnI and cTnT. Using a novel pair of monoclonal antibodies, we generated a sensitive assay for MyC on the Erenna platform (Singulex) and compared serum concentrations with those of cTnI (Abbott) and cTnT (Roche) in stable ambulatory cardiac patients without evidence of acute cardiac injury or significant coronary artery stenoses. The assay for cMyC had a lower limit of detection of 0.4 ng/L, a lower limit of quantification (LLoQ) of 1.2 ng/L (LLoQ at 20% coefficient of variation [CV]) and reasonable recovery (107.1 ± 3.7%; mean ± standard deviation), dilutional linearity (101.0 ± 7.7%), and intraseries precision (CV, 11 ± 3%) and interseries precision (CV, 13 ± 3%). In 360 stable patients, cMyC was quantifiable in 359 patients and compared with cTnT and cTnI measured using contemporary high-sensitivity assays. cMyC concentration (median, 12.2 ng/L; interquartile range [IQR], 7.9-21.2 ng/L) was linearly correlated with those for cTnT (median, <3.0 ng/L; IQR, <3.0-4.9 ng/L; R = 0.56, P < 0.01) and cTnI (median, 2.10 ng/L; IQR, 1.3-4.2 ng/L; R = 0.77, P < 0.01) and showed similar dependencies on age, renal function, and left ventricular function. We have developed a high-sensitivity assay for cMyC. Concentrations of cMyC in clinically stable patients are highly correlated with those of cTnT and cTnI. This high correlation may enable ratiometric comparisons between biomarkers to distinguish clinical instability.

Coagulation Biomarkers in Healthy Chinese-Origin Rhesus Macaques (Macaca mulatta)

Rhesus macaques (Macaca mulatta) are a common model for the study of human biology and disease. To manage coagulopathies in these animals and to study their clotting changes, the ability to measure coagulation biomarkers is necessary. Currently, few options for coagulation testing in NHP are commercially available. In this study, assays for 4 coagulation biomarkers-D-dimer, antithrombin III, protein C, and soluble P-selectin-were developed and optimized for rhesus macaques. Whole blood was collected from 28 healthy Chinese-origin rhesus macaques (11 male; 17 female) ranging in age from 5 to 20 y. Coagulation biomarkers were measured by using bead-based sandwich ELISA technology. The ranges (mean ± 90% confidence interval) for these biomarkers were: antithrombin III, 124.2 to 133.4 μg/mL; protein C, 3.2 to 3.6 μg/mL; D-dimer, 110.3 to 161.3 ng/mL; soluble P-selectin, 0.12 to 0.14 ng/10(6) platelets. These reference values did not differ significantly according to sex or age. These new assays for coagulation biomarkers in rhesus macaques will facilitate the evaluation of in vivo hemostasis.

Antemortem Screening for Left Ventricular Hypertrophy in Rhesus Macaques (Macaca mulatta)

Concentric left ventricular hypertrophy (LVH) is a hallmark finding in hypertrophic cardiomyopathy that leads to diastolic dysfunction and variable cardiac consequences as severe as congestive heart failure and sudden cardiac death. LVH was diagnosed postmortem in a large colony of rhesus macaques (Macaca mulatta), but methods to screen and diagnose LVH in living animals are desired. We hypothesized that targeted echocardiography of macaques with a familial association of LVH would yield antemortem LVH diagnoses. We also hypothesized that cardiac biomarker levels would be higher in sudden-death LVH or occult LVH than controls and that cardiac troponin I (cTnI) levels would be higher in macaques housed outdoors than indoors. Sera were assayed for cardiac biomarkers (cTnI, C-reactive protein, creatinine kinase-MB, creatine phosphokinase, and LDH), in conjunction with echocardiography, after diagnosis by postmortem exam or from animals with different levels of exercise due to indoor compared with outdoor housing. None of the investigated biomarkers were associated with LVH. cTnI levels were significantly higher in serum collected from outdoor than indoor macaques. In addition, LVH was diagnosed in 29.4% of subjects with a familial association of LVH. These findings suggest that exercise may increase cTnI levels in rhesus macaques and that targeted echocardiography of rhesus macaques with a familial association of LVH was the most useful variable examined for disease surveillance.

Effects of diet-induced obesity on metabolic parameters and reproductive function in female Ossabaw minipigs

This study characterizes the effect of an excess-calorie, high-fat, high-cholesterol, high-fructose diet on metabolic parameters and reproductive function in female Ossabaw minipigs. Cycling sows were fed a hypercaloric, high-fat, high-cholesterol, and high-fructose diet (obese, n = 4) or a control diet (control, n = 5) for 13 mo. During the final 4 mo, ovarian ultrasonography was done, blood was collected, and weights and measures were taken. Pigs then underwent ovarian stimulation. Cycle length and androstenedione, total testosterone, progesterone, estradiol, follicle-stimulating hormone, luteinizing hormone, insulin, fructosamine, lipid, and glucose levels were measured. In addition, adipose tissue aromatase gene expression was assessed. As compared with control pigs, obese pigs were hyperglycemic and hyperinsulinemic; had elevated total cholesterol, triglyceride, and leptin levels, and demonstrated abdominal adiposity. Visceral adipose tissue of obese pigs, as compared with control pigs, showed increased aromatase gene expression. Obese pigs had longer estrous cycles, higher serum androstenedione, and higher luteal phase serum luteinizing hormone, compared with control pigs. During the luteal phase, obese pigs had more medium, ovulatory, and cystic ovarian follicles, whereas control pigs had more small ovarian follicles. When fed an excess-calorie, high-fat, high-cholesterol, high-fructose diet, female Ossabaw minipigs develop obesity, metabolic syndrome, and abnormal reproductive function. This animal model may be applicable to studies of the effects of obesity on fertility in women.

Characterization of ovarian aging and reproductive senescence in vervet monkeys (Chlorocebus aethiops sabaeus)

Female vervet monkeys (Chlorocebus aethiops sabaeus) are used as an experimental model for chronic diseases relevant to women's health. However, reproductive senescence (menopause) has not yet been characterized for vervet monkeys. Here we describe the histologic, hormonal, and menstrual markers of reproductive senescence in vervet monkeys from the Wake Forest Vervet Research Colony. Ovaries from monkeys (age, 0 to 27 y) were serially sectioned (5 μm), stained, and photographed. In every 100th section, the numbers of primordial, primary, and secondary follicles were determined, and triplicate measurements were used to calculate mean numbers of follicles per ovary. Antimüllerian hormone (AMH), follicle stimulating hormone, and menstrual cycle length were measured in additional monkeys. Primordial follicles and AMH decreased significantly with age, and significant correlations between numbers of primordial and primary follicles and between numbers of primary and secondary follicles were noted. Histologic evaluation revealed that ovaries from 4 aged monkeys (older than 23 y) were senescent. One aged monkey transitioned to menopause, experiencing cycle irregularity over 4 y, eventual cessation of menses, and plasma AMH below the level of detection. Finally, with increasing age, the percentage of female vervets with offspring declined significantly. The present study provides insight into ovarian aging and reproductive senescence in vervet monkeys. Results highlight the importance of considering this nonhuman primate as a model to investigate the relationships between ovarian aging and chronic disease risk.

Peri-conceptional changes in maternal exposure to sewage sludge chemicals disturbs fetal thyroid gland development in sheep

Ewes were exposed to sewage sludge-fertilized pastures in a study designed investigate pre-conceptual and/or gestational exposure to environmental chemicals. The in utero impact on fetal thyroid morphology and function at day 110 (of 145) of pregnancy was then determined. Pre-conceptual exposure increased the relative thyroid organ weights in male fetuses. The number of thyroid follicles in thyroids of fetuses after pre-conceptual or gestational exposure was reduced. This correlated with an increase in Ki67 positive cells. Pre-conceptual exposure to sewage sludge reduced small blood vessels in fetal thyroids. Thyroid tissues of exposed fetuses contained regions where mature angio-follicular units were reduced exhibiting decreased immunostaining for sodium-iodide symporter (NIS). Fetal plasma levels of fT3 and fT4 in exposed animals, however, were not different from controls suggesting compensatory changes in the thyroid gland to maintain homeostasis in exposed fetuses. The regional aberrations in thyroid morphology may impact on the post-natal life of the exposed offspring.

Acoustic over-exposure triggers burst firing in dorsal cochlear nucleus fusiform cells

Acoustic over-exposure (AOE) triggers deafness in animals and humans and provokes auditory nerve degeneration. Weeks after exposure there is an increase in the cellular excitability within the dorsal cochlear nucleus (DCN) and this is considered as a possible neural correlate of tinnitus. The origin of this DCN hyperactivity phenomenon is still unknown but it is associated with neurons lying within the fusiform cell layer. Here we investigated changes of excitability within identified fusiform cells following AOE. Wistar rats were exposed to a loud (110 dB SPL) single tone (14.8 kHz) for 4 h. Auditory brainstem response recordings performed 3-4 days after AOE showed that the hearing thresholds were significantly elevated by about 20-30 dB SPL for frequencies above 15 kHz. Control fusiform cells fired with a regular firing pattern as assessed by the coefficient of variation of the inter-spike interval distribution of 0.19 ± 0.11 (n = 5). Three to four days after AOE, 40% of fusiform cells exhibited irregular bursting discharge patterns (coefficient of variation of the inter-spike interval distribution of 1.8 ± 0.6, n = 5; p < 0.05). Additionally the maximal firing following step current injections was reduced in these cells (from 83 ± 11 Hz, n = 5 in unexposed condition to 43 ± 6 Hz, n = 5 after AOE) and this was accompanied by an increased firing gain (from 0.09 ± 0.01 Hz/pA, n = 5 in unexposed condition to 0.56 ± 0.25 Hz/pA, n = 5 after AOE). Current and voltage clamp recordings suggest that the presence of bursts in fusiform cells is related to a down regulation of high voltage activated potassium currents. In conclusion we showed that AOE triggers deafness at early stages and this is correlated with profound changes in the firing pattern and frequency of the DCN major output fusiform cells. The changes here described could represent the initial network imbalance prior to the emergence of tinnitus.

Characterization of a TiO₂ enrichment method for label-free quantitative phosphoproteomics

Phosphorylation is a protein post-translational modification with key roles in the regulation of cell biochemistry and signaling. In-depth analysis of phosphorylation using mass spectrometry is permitting the investigation of processes controlled by phosphorylation at the system level. A critical step of these phosphoproteomics methods involves the isolation of phosphorylated peptides from the more abundant unmodified peptides produced by the digestion of cell lysates. Although different techniques to enrich for phosphopeptides have been reported, there are limited data on their suitability for direct quantitative analysis by MS. Here we report a TiO(2) based enrichment method compatible with large-scale and label-free quantitative analysis by LC-MS/MS. Starting with just 500 μg of protein, the technique reproducibly isolated hundreds of peptides, >85% of which were phosphorylated. These results were obtained by using relatively short LC-MS/MS gradient runs (45 min) and without any previous separation step. In order to characterize the performance of the method for quantitative analyses, we employed label-free LC-MS/MS using extracted ion chromatograms as the quantitative readout. After normalization, phosphopeptides were quantified with good precision (coefficient of variation was 20% on average, n=900 phosphopeptides), linearity (correlation coefficients >0.98) and accuracy (deviations <20%). Thus, phosphopeptide ion signals correlated with the concentration of the respective phosphopeptide in samples, making the approach suitable for in-depth relative quantification of phosphorylation by label-free LC-MS/MS.

Effect of body position on limb lead electrocardiographic findings in sedated cynomolgus macaques (Macaca fascicularis)

Electrocardiograms (ECGs) often are collected from sedated cynomolgus macaques (Macaca fascicularis) in drug safety studies to support investigational new drug applications. ECGs are evaluated either manually or electronically, and the quality of the ECG tracing can affect the quality of that evaluation. The body position of the subject sometimes is manipulated to eliminate noise or clarify ECG complex morphology, and typically multiple technicians collect ECG data over time. Both factors-body position and multiple technicians-could affect ECG quality. This study was designed to determine whether body position or multiple technicians affects heart rate, mean electrical axis, or ECG parameters (RR interval, P wave duration, PR interval, QRS duration, QT interval (uncorrected and rate-corrected by using the Bazett [QTcb] and Fridericia [QTcf] formulas), P wave amplitude, R wave amplitude, T wave height, T wave height negative, and ST segment elevation). The results reveal minimal (coefficient of variation [CV] less than 10%) within-animal variation between body positions (ventral, dorsal, right or left lateral), with the exception of P wave amplitude (17.5%), R wave amplitude (23.7%), and ST segment elevation (43%). Minimal variation in ECG parameters (no more than 7%) was detected between technicians, across animals, and across body positions. These findings suggest that neither a change in body position to increase the quality of an ECG tracing nor the use of multiple technicians significantly affect the evaluation of quantitative ECG parameters, especially QTcb (0.1% CV) and QTcf (1.3% CV).

Relationship of volumetric bone density and structural parameters at different skeletal sites to sex steroid levels in women

CONTEXT

Although estrogen clearly plays a central role in regulating bone mass in women, studies in men have suggested that there may be a threshold bioavailable (bio) estradiol (E2) level below which aging men begin to lose bone and that the threshold for estrogen deficiency in cortical bone may be considerably lower than that in trabecular bone. There are no data testing this in women.

OBJECTIVE

Our objective was to assess volumetric bone mineral density (vBMD) and bone geometry by quantitative computed tomography and relate these to circulating bio E2 and bio testosterone levels.

DESIGN

We studied a cross-sectional, age-stratified population sample of 235 women (age, 21-97 yr).

RESULTS

vBMD/structural parameters were not related to sex steroid levels in young premenopausal women (age, 20-39 yr) with a median bio E2 level of 17 pg/ml (63 pmol/liter). By contrast, bio E2 and bio testosterone levels were both significantly associated with trabecular and cortical vBMD and cortical area at multiple sites in late postmenopausal women (age > or = 60 yr) who had a median bio E2 level of 3 pg/ml (11 pmol/liter). Late premenopausal and early postmenopausal women (age, 40-59 yr) with an intermediate median bio E2 level of 11 pg/ml (42 pmol/liter) showed age-adjusted correlations of bio E2 levels with trabecular but not with cortical vBMD.

CONCLUSIONS

In women, bio E2 levels are associated with vBMD and some structural bone parameters at low but not high bio E2 levels. Similar to findings in men, the threshold for estrogen deficiency in cortical bone in women appears to be lower than that in trabecular bone.

The Diabetes Prevention Program: baseline characteristics of the randomized cohort. The Diabetes Prevention Program Research Group

OBJECTIVE

The Diabetes Prevention Program (DPP) is a 27-center randomized clinical trial designed to evaluate the safety and efficacy of interventions that may delay or prevent development of diabetes in people at increased risk for type 2 diabetes.

RESEARCH DESIGN AND METHODS

Eligibility requirements were age > or = 25 years, BMI > or = 24 kg/m2 (> or = 22 kg/m2 for Asian-Americans), and impaired glucose tolerance plus a fasting plasma glucose of 5.3-6.9 mmol/l (or < or = 6.9 mmol for American Indians). Randomization of participants into the DPP over 2.7 years ended in June 1999. Baseline data for the three treatment groups--intensive lifestyle modification, standard care plus metformin, and standard care plus placebo--are presented for the 3,234 participants who have been randomized.

RESULTS

Of all participants, 55% were Caucasian, 20% were African-American, 16% were Hispanic, 5% were American Indian, and 4% were Asian-American. Their average age at entry was 51 +/- 10.7 years (mean +/- SD), and 67.7% were women. Moreover, 16% were < 40 years of age, and 20% were > or = 60 years of age. Of the women, 48% were postmenopausal. Men and women had similar frequencies of history of hypercholesterolemia (37 and 33%, respectively) or hypertension (29 and 26%, respectively). On the basis of fasting lipid determinations, 54% of men and 40% of women fit National Cholesterol Education Program criteria for abnormal lipid profiles. More men than women were current or former cigarette smokers or had a history of coronary heart disease. Furthermore, 66% of men and 71% of women had a first-degree relative with diabetes. Overall, BMI averaged 34.0 +/- 6.7 kg/m2 at baseline with 57% of the men and 73% of women having a BMI > or = 30 kg/m2. Average fasting plasma glucose (6.0 +/- 0.5 mmol/l) and HbA1c (5.9 +/- 0.5%) in men were comparable with values in women (5.9 +/- 0.4 mmol/l and 5.9 +/- 0.5%, respectively).

CONCLUSIONS

The DPP has successfully randomized a large cohort of participants with a wide distribution of age, obesity, and ethnic and racial backgrounds who are at high risk for developing type 2 diabetes. The study will examine the effects of interventions on the development of diabetes.