Does mean arterial blood pressure scale with body mass in mammals? Effects of measurement of blood pressure.

For at least the last 30 years, it has been discussed whether mean arterial blood pressure (MAP) is independent of body mass or whether it increases in accordance with the vertical height between the heart and the brain. The debate has centred on the most appropriate mathematical models for analysing allometric scaling and phylogenetic relationships; there has been previously little focus on evaluating the validity of underlying physiological data. Currently, the 2 most comprehensive scaling analyses are based on data from 47 species of mammals, based on 114 references. We reviewed all available references to determine under which physiological conditions MAP had been recorded. In 44 (38.6%) of the cited references, MAP was measured in anaesthetized animals. Data from conscious animals were reported in 59 (51.8%) of references; of these, 3 (2.6%) were radiotelemetric studies. In 5 species, data were reported from both anaesthetized and conscious animals, and the mean difference in the MAP between these settings was 20 ± 29 mm Hg. From a literature search, we identified MAP measurements performed by radiotelemetry in 11 of the 47 species included in the meta-analyses. A Bland-Altman analysis showed a bias of 1 mm Hg with 95% confidence interval (from -35 to 36 mm Hg); that is, the limits of agreement between radiotelemetric studies and studies in restrained animals were double the supposed difference in the MAP between the mouse and elephant. In conclusion, the existing literature does not provide evidence for either a positive or neutral scaling of arterial pressure to body mass across taxa.

Altered inflammatory response and increased neurodegeneration in metallothionein I+II deficient mice during experimental autoimmune encephalomyelitis.

Metallothionein-I+II (MT-I+II) are antioxidant, neuroprotective proteins, and in this report we have examined their roles during experimental autoimmune encephalomyelitis (EAE) by comparing MT-I+II-knock-out (MTKO) and wild-type mice. We herewith show that EAE susceptibility is higher in MTKO mice relatively to wild-type mice, and that the inflammatory responses elicited by EAE in the central nervous system (CNS) are significantly altered by MT-I+II deficiency. Thus, during EAE the MTKO mice showed increased macrophage and T-lymphocytes infiltration in the CNS, while their reactive astrogliosis was significantly decreased. In addition, the expression of the proinflammatory cytokines interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha elicited by EAE was further increased in the MTKO mice, and oxidative stress and apoptosis were also significantly increased in MTKO mice compared to normal mice. The present results strongly suggest that MT-I+II are major factors involved in the inflammatory response of the CNS during EAE and that they play a neuroprotective role in this scenario.

No impact of blood pressure variability on microalbuminuria and left ventricular geometry: analysis of daytime variation, diurnal variation and 'white coat' effect.

OBJECTIVE: To investigate the influence of blood pressure variability on target organ involvement. METHODS: Using a cross-sectional study of a hypertension clinic at a district general hospital, 420 patients with newly diagnosed untreated essential hypertension referred on a consecutive basis from general practice and 146 normal subjects drawn at random from the Danish National Register underwent a variety of measurements which included: echocardiography with determination of left ventricular mass index and relative wall thickness and early morning urine albumin/creatinine ratio. Mean, standard deviation and coefficient of variation of automated clinic values; daytime, night-time and full 24-h period were extracted from 24-h ambulatory blood pressure (ABP) monitoring. 'White coat' effect and dip were calculated. Hypertensives were classified into subjects with high or low variability, into 'white coat' hypertensives or established hypertensives and into dippers or non-dippers. RESULTS: Standard deviation of daytime blood pressure (BP) was positively associated with target organ damage and BP level, which was not the case when variability was expressed as a coefficient of variation. Patients with high variability exhibited no more significant target organ damage than patients with low variability, but patients with established hypertension had significantly more target organ damage than the 'white coat' hypertensives. The 'white coat' effect as such was not associated with increased target organ involvement. Non-dippers had significantly more cardiac target organ damage than dippers, but the difference disappeared after correction for different 24-h BP level. CONCLUSION: BP variability data obtained by non-invasive ABP monitoring does not seem to improve the information inherent in the BP level.