Role of sympathetic nerve fibers in hemodynamic responses to stress in rats]

Hemodynamic responses to acute stress exposure were studied in normotensive control (C) and chronically sympathectomized (S) rats. Male Sprague-Dawley rats received daily sc injections of either saline (C) or guanethidine (S) from 1 to 13 weeks of age. Doppler flow probes were then implanted for the measurement of blood velocity in the sub-diaphragmatic aorta, superior mesenteric artery and distal aorta (hindquarters). After 10 days of recovery and 24 hours before the study, the caudal artery was cannulated. In the conscious freely moving rats, mean arterial pressure (MAP), heart rate (HR) and indices of regional blood flows and vascular conductances (G as blood flow/MAP ratio) were recorded beat to beat, before and during emotional stress (jet of air for 2 min). In basal conditions, mean values of MAP and HR were similar in C (107 +/- 2 mmHg; 399 +/- 8 bpm, n = 9) and S (106 +/- 3 mmHg; 384 +/- 12 bpm, n = 7) rats. The effects of stress on MAP, HR, aortic (AoG), mesenteric (MeG) and hindquarters (HqG) vascular conductances are expressed as percentage changes from baseline (delta): [table: see text] These results highlight the role of vascular sympathetic nerves in pressor responses and systemic and mesenteric vasoconstrictions induced by stress in the rat. They also indicate that vasodilatation in the hindquarters vascular bed is not secondary to withdrawal of sympathetic vasoconstrictor tone but rather to active phenomena which do not involve the stimulation of vascular beta 2-adrenoceptors by neuronal catecholamines nor the release of vasodilator cotransmitters from the sympathetic nerve endings.     

Prevalence of breast arterial calcifications in an ethnically diverse population of women

PURPOSE: Breast arterial calcifications (BAC) identified on routine mammography have been associated with coronary heart disease (CHD) risk factors including diabetes and hypertension, angiographically defined CHD, and increased cardiovascular mortality. Accumulating evidence suggests that the mammogram may be an important tool to identify women at risk for CHD, however, the epidemiology of BAC has been poorly defined and previous studies limited to white populations. METHODS: The mammograms of 1905 consecutive women (51.2% Hispanic, 25.8% white, 15.3% black, 5.4% other, 2.2% Asian, ages 35-92 years) were evaluated for the presence of BAC and the number of calcified arteries. RESULTS: The overall prevalence of BAC was 29.4% and was significantly higher for Hispanics compared with whites (34.5% vs. 24.0%, p=0.0002) and lower for Asians compared with whites (7.1% vs. 24.0%, p < 0.02). Among BAC-positive women aged 65 years or less, blacks had more calcified arteries than whites (p < 0.01). The presence of BAC increased with age (p for trend < 0.0001). In age-adjusted models, older Hispanics were more likely to be BAC-positive than whites of similar age (p < 0.02). CONCLUSION: These results indicate that BAC varies significantly by age and race/ethnicity. These findings should be taken into consideration when designing future studies of BAC and CHD.     

Computerized analysis of cardiovascular activity in the conscious unrestrained rat. Application to the study of a new antihypertensive agent

A more precise knowledge of cardiovascular activity in rats needs its direct recording for long periods of time, in conscious unrestrained animals. A system has been developed, which allows direct recording of blood pressure (BP) in freely moving rats, by means of a floating catheter chronically inserted in the abdominal aorta, connected to a rotating swivel, and then to a pressure transducer. A mini-computer performs on-line processing of BP curves, and stores the values of 5 cardiovascular parameters on hard disk: systolic, diastolic and mean arterial pressures, heart rate and dp/dt max. Off line processing allows graphic and statistical analysis of the data. Simultaneously recording from two rats is very useful in pharmacology because a treated animal and a control one are studied at the same time and in the same conditions. This methodology was used to evaluate the effects of a chronic treatment (2 mg/kg, ip, during 8 days) and of single injections (0.5 and 3 mg/kg, iv) of a new antihypertensive substance, CM 40441a, in 15 W old males SHR.     

Interpretation of drug concentrations in an alternative matrix: the case of meprobamate in bile

Investigating toxicological causes of death may require alternative matrices when the usual ones are lacking. Whereas forensic toxicology uses bile almost only for xenobiotic screening, a diagnostic test interpreting postmortem bile concentrations of meprobamate is reported. Based on 128 sets of autopsy data, its intrinsic qualities were good, with 0.95 sensitivity and 0.93 specificity. In a French forensic population, the positive and negative predictive factors were 0.90 and 0.97, respectively. It is a useful means of revealing overdoses where blood samples are not available or of confirming blood tests when postmortem redistribution is suspected.     

The relation of blood pressure to coronary heart mortality in different age groups varies by ethnicity

BACKGROUND: The relative importance of pulse pressure, mean arterial pressure, systolic blood pressure (SBP), and diastolic blood pressure (DBP) as predictors of coronary heart disease (CHD) have been shown to change with aging in individuals of white ethnicity, but few published data exist for those of African American ethnicity. METHODS: To assess the role of ethnicity in this relationship we compared the association of BP indices to CHD mortality (from a pooled database of eight prospective cohorts, n = 29829, follow-up 13.8 +/- 7.9 years, 1912 events) in the four age groups (30 to 39, 40 to 49, 50 to 59, and > or = 60 years) by the decrease in the -2 log likelihood in Cox regression analyses of subjects who were not receiving antihypertensive drug therapy at baseline. RESULTS: All BP indices were significant (P < .05) for all age groups in models containing a single BP index. In white subjects, the best predictor of CHD mortality was DBP for persons 30 to 39 years of age, whereas SBP was the best predictor for persons 40 to 49, 50 to 59 and > or = 60 years of age. In African American subjects, SBP was the best predictor in all age groups. When considered jointly, DBP, but not SBP, was significantly associated with CHD mortality in white subjects 30 to 39 years of age. Only SBP was significant in white subjects 40 to 49, 50 to 59, and > or = 60 years of age. In African Americans, SBP, but not DBP, was associated with CHD mortality in all four age groups when both were in the model. CONCLUSION: In African American subjects, SBP was found to be a better predictor of CHD mortality than DBP or pulse pressure. In white subjects, there was a shift in importance from DBP to SBP as predictors of CHD mortality from the 30 to 39-year age group to the older groups.     

Role of sympathetic nervous system on blood pressure and heart rate variabilities in the rat: spectral analysis

The role of the sympathetic nervous system (SNS) in the genesis of the beat-to-beat variability of blood pressure (BP) and heart rate (HR) was studied using spectral analysis. The SNS activity of genetically normotensive rats of the Lyon strain (LN) was abolished in 2 ways: 1) adrenergic blockade with administrations of phentolamine (PHE, 5 mg/kg i.v.) or propranolol (PRO, 5 mg/kg i.v.) or both drugs (PHEPRO) or 2) destruction of the sympathetic fibers with an early chronic treatment with guanethidine (LNSx). HR and systolic (SBP) and diastolic (DBP) BP spectra were computed using 50 to 100 stationary sequences from 1 h beat-to-beat recordings and covered the 0.015-3.85 Hz frequency band. In LN rats, spectra obtained in baseline conditions exhibited a high-frequency peak (HF, 1.04-1.13 Hz) related to the respiratory frequency and a mid-frequency peak (MF, 0.38-0.45 Hz). Concerning BP, the alterations of the SNS induced significant decreases of the total modulus (mmHg/Hz1/2) of the MF band (0.27-0.74 Hz): [formula: see text] In addition, the MF peak of SBP and DBP spectra was abolished in LNSx and PHEPRO rats. Concerning HR spectra, the moduli of all the frequency components were decreased in PHEPRO rats only. In conclusion, the similarity of the results observed in LNSx and PHEPRO rats shows that the MF oscillations of BP depend in a large extent (65%) on the action of the sympathetic fibers and involve the activation of both alpha- and beta-adrenoceptors. Concerning DBP, this effect is especially mediated by the activation of alpha-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)