体积 3, 问题 3 (2014)


Oscillator Suppression in the Blood Flow Regulation of Interacting, Non- Identical Nephrons

Yulia P Emelianova, Alexander P Kuznetsov, Jakob L Laugesen, Erik Mosekilde and Niels-Henrik Holstein-Rathlou

Background: Regulation of the blood flow to the individual functional unit (nephron) of the kidney involves a feedback mechanism that produces large-amplitude oscillations in the blood flow itself as well as in the intra-nephron pressures and flows. Neighboring nephrons adjust their blood flow variations relative to one another via signals that propagate along the interconnecting blood vessels.

Purpose and method: Using a detailed physiological-based model of a pair of vascular coupled, non-identical nephrons, the paper examines the effect that their relative oscillatory strength has on the behavior of the coupled system. This is of direct interest in connection with ongoing work attempting to study the synchronization behavior for larger groups of superficial nephrons by means of laser speckle contrast imaging.

Results: Our analysis demonstrates that a region of so-called “broadband Synchronization” may develop between those coupling strengths at which the stronger oscillating nephron starts to suppress the autonomous oscillations of the weaker nephron and those coupling strengths at which the two nephrons mutually inhibit each other’s oscillations. We suggest that the transition be-tween synchronized and suppressed dynamics may have a physiological significance comparable to the transition from ergodic to synchronized periodic dynamics.


Baroreflex Sensitivity in Relation to Clinical Characteristics in Subject Aged 40 to 80 Years

Louise Brinth, Kirsten Pors, Tabassam Latif, Andreas Kjær and Jesper Mehlsen

Baroreflex function measured as baroreflex sensitivity (BRS) mirrors an integrated capacity of the autonomic nervous system. We aimed to assess the relationship between measures of BRS and age and relevant clinical characteristics.

80 subjects participating in the Copenhagen City Heart study (43 women) with a mean age of 59 ± 11 years (range 41-79 years) were included. Baroreceptor activity was quantified through the Valsalva manoeuvre (VM) and as a spontaneous function. BRS was tested against age, gender, smoking status, body size and predicted risk of coronary heart disease based on the Framingham score.

BRS was found to decline with age, but this change disappeared when correcting for the age related increase in systolic blood pressure. We found that the VM-derived indices of sympathetic vascular control declined with age as did the vagally controlled heart rate changes in response to deep breathing and VM. We could not demonstrate any correlation between BRS, smoking status, and body size when adjusting for age and gender, whereas spontaneous BRS was reduced with increasing Framingham risk score. Principal component analysis revealed three component explaining 69% of the total variance in our population comprising one component reflecting the sympathetic activity, the parasympathetic system, and the integrated spontaneous BRS, respectively. The parasympathetic component was the only one correlating with clinical characteristics of declining age, smoking habits, systolic blood pressure and Framingham score.

It is concluded that the parasympathetic and sympathetic parts of the baroreflex arch behave differently with respect to aging and cardiovascular risk factors. The most prominent changes are seen in cardiovagal control whereas the effects of age related changes in sympathetic vascular control are less noticeable. Our study supports the use of the cardiovagal part of the baroreflex arch as an indicator of cardiovascular risk.


Relationship between Nocturnal Blood Pressure and Left Ventricular Hypertrophy in Hypertensive Patients

Hang Zhu, Wei Zhang, Yajun Shi, Yiming Ma, Yunfeng Han, Jie Liu and Hao Xue

Objective: Left ventricular hypertrophy (LVH) is the most common target organ damage in hypertension. However, the association of LVH and circadian rhythm of blood pressure (BP) is unknown. The objective of the present study was to explore the relationship between circadian rhythm of BP and LVH using ambulatory blood pressure monitoring (ABPM).

Study design: A total of 325 untreated hypertensive patients were recruited. The patients were divided into two groups: hypertensive patients with LVH (n=121) and without LVH (n=204). Twenty-four-hour ABPM was performed in all the patients to collect the following parameters: 24-hour average systolic and diastolic pressure, daytime average systolic and diastolic pressure, nocturnal average systolic and diastolic pressure, and night to day BP ratio. The relationship between LVH and the various ABPM parameters was analyzed.

Results: We found that the average nocturnal systolic blood pressure (SBP) in hypertensive patients with LVH was higher than that in hypertensive patients without LVH (145 ± 16.1 mmHg versus 136 ± 12.7 mmHg, P<0.05). The average night to day SBP ratio in hypertensive patients with LVH was also higher than that in hypertensive patients without LVH (0.93 ± 0.04 versus 0.86 ± 0.04, P<0.05). Multiple regression analysis indicate that the average nocturnal SBP and the night to day SBP ratio were associated with LVH (Odds ratio (OR) 1.67, 95% CI: 1.31-3.21; OR: 1.88, 95% CI: 1.56-3.78) by adjustment for traditional covariates.

Conclusion: The average nocturnal SBP and the average night-day SBP ratio are independent risk factors of LVH in patients with hypertension.


Increased Physical Activity Reduces the Odds of Elevated Systolic Blood Pressure Independent of Body Mass or Ethnicity in Rural Adolescents

Rudy M. Ortiz, Ruben Rodriguez, Sarah Depaoli and Simón E Weffer

Objectives: Reduced Physical Activity (PA) has been implicated in the increased prevalence of adolescent obesity and Systolic Blood Pressure (SBP). The present study provides a robust examination of these relationships in Hispanic adolescents from a rural population for which data are scarce.

Methods: We compared PA levels, SBP and body mass categories (normal weight, overweight and obese) between non-Hispanic white and Hispanic adolescents (15 ± 0.1 yrs; n=983 males, 911 females) using odds ratio and path analyses.

Results: When groups (by gender & ethnicity) were categorized by body mass independent of SBP, prevalence of elevated SBP for obese compared to normal weight cohorts was 3.5- and 12-fold greater for non-Hispanic white males and females, respectively, and 2- and 3-fold greater for Hispanic males and females, respectively. When categorized by SBP independent of Body Mass Index (BMI), prevalence of obesity for adolescents with elevated SBP compared to normotensive cohorts was 3.5- and 6-fold greater for non-Hispanic white males and females, respectively, and 2-fold greater for both Hispanic males and females.

Conclusions: Path analyses suggest that both reduced PA and increased BMI are simultaneous predictors of the observed elevation in SBP. Odds ratio analyses revealed that 6+hr PA/wk reduced the probability of developing elevated SBP 3-fold in both genders independent of body mass category or ethnicity, identifying increased PA as a critical behavioral element to target to alleviate the consequences of obesity-related increases in SBP in young people regardless of ethnicity or gender.


Sudden Onset of Pyrexia and Severe Blood Pressure Elevation Due to IL-6 Production by Pheochromocytoma

Takashi Ando, Satoshi Morimoto, Yuki Mizuguchi, Akimi Okamoto, Masaki Ryuzaki, Yoichi Oshima, Daisuke Watanabe, Fumiko Kawakami-Mori, Masami Ono, Tatsuo Sawada, Sho Ono, Takumi Igarashi, Hitoshi Kaya and Atsuhiro Ichihara

We report a case of pheochromocytoma presenting with a sudden change in clinical manifestation. The change in the serum Interleukin-6 (IL-6) and histological examination indicated that this clinical presentation was caused by IL-6 elevation secondary to pheochromocytoma. This rare tumor should be considered in the differential diagnosis of fever of unknown origin, and prompt and appropriate administration of an alpha-1 blocker is highly recommended, especially for patients with large pheochromocytomas.


Dual Blocking of the Renin Angiotensin System: A Settled Issue?

Luis I Juncos and Caputo Joaquin

The renin-angiotensin system (RAS) exerts wide-ranging effects on cardiovascular and kidney function. Oddly, this system that was designed to preserve normal hemodynamics may become harmful in certain clinical situations. For this reason, RAS inhibition is a highly effective therapeutic approach, not only to lower blood pressure but also to reduce kidney and cardiovascular disease morbidity and mortality. In some patients however, these beneficial effects of RAS inhibition are incomplete or absent. For these less than ideal results, several reasons have been proposed; e.g.: angiotensin escape, over production of angiotensin from negative feedback, local tissue RAS, etc. To secure better RAS blocking, some clinicians have proposed increasing the dose of angiotensin converting enzyme inhibitors (ACEi) or angiotensin II receptor blockers (ARB’s) beyond the recommended doses or combining two RAS inhibitors. In high-risk patients though, this more intensive RAS inhibition should be undertaken with great precaution, as tissue perfusion may be highly renin-dependent and serious adverse side effects could take place. This issue is yet to be settled as patients with significant proteinuria can be benefitted by intensive RAS inhibition. The purpose of this article is to review the evidences accrued on the use of intensive or dual blocking of RAS. We analyze potential purposes and hazards in the light of actual population data as published in recent trials.


Silent Crisis: Epidemic Hypertension in Rural West Africa

Emmanuel Ato Williams, Daniel Ansong, Stephen Alder, Lowell Scott Benson, Stephen James Campbell, Katherine MacDonald, Tadashi R Miya, Isaac Boakye, Joseph Marfo Boaheng, Evans Xorse Amuzu, Osei Asibey Owusu, Isaac Nyanor, Bernard Arhin and Ty Triston Dickerson

Background: Hypertension is the commonest modifiable risk factor of cardiovascular diseases and a major preventable cause of premature mortality. The worldwide prevalence of hypertension will increase by more than half by 2025; almost three-quarters of people with hypertension will be living in developing countries by 2025. We set out to evaluate the burden and correlates of adult hypertension in a rural Ghanaian community.

Methods: A cross-sectional survey was conducted on 438 adults aged ≥35 in the Barekese sub-district (estimated population 18,510). Socio-demographic characteristics, modifiable and non-modifiable risk factors, blood pressure (BP) and anthropometric measurements were collected using standardized protocols.

Results: The proportion of hypertension and isolated systolic hypertension in the study population is 50.9% and 16.0% respectively. Only 21.2% were previously diagnosed as hypertensive; 25.8% of whom were not being treated. The proportion of the people with hypertension whose BPs were controlled (<140/90mmHg) was 13.5%. The mean systolic and diastolic BPs were 134.75 mmHg (SD: 24.68) and 83.01 mmHg (SD: 13.58). Obesity (Body Mass Index, BMI>30 kg/m2) was found in 13.24% of the population, with 6.7% being extremely obese (BMI>40 kg/m2). Factors such as increasing age and BMI positively correlated with BP.

Conclusion: There appears to be a high burden of hypertension in rural Ghana; the low detection, and poor management and control should make this a high priority. These findings indicate the need for urgent measures to promote health education that would facilitate prevention, early detection, and management of hypertension.


Function and Protein Expression of Potassium Channels in Mesenteric Resistance Arteries Isolated from 2K-1C Hypertensive Rats

Alice V Araújo, Marcella D Grando, Roberto S DA Silva and Lusiane M Bendhack

The present study aimed to evaluate the K+ channels activation in vascular relaxation induced by the nitric oxide (NO) donors ruthenium-derived complex (Terpy) and sodium nitroprusside (SNP), as well as its protein expression, on mesenteric resistance arteries (MRA) isolated from renal hypertensive rats (2K-1C) and sham-operated rats (Sham). The NO donors Terpy and SNP induced relaxation with similar efficacy in isolated MRA from both 2K-1C and Sham rats, although SNP was more potent than Terpy. The maximum relaxation induced by Terpy was decreased when the voltagegated potassium channels were blocked in MRA from Sham, but not in 2K-1C rat arteries. The blockade of ATP-sensitive (KATP), big and small conductance Ca2+-activated (SKCa) or inward rectifier (KIR) potassium channels decreased the maximum relaxation induced by Terpy in MRA from Sham and 2K-1C rats. However, the maximum relaxation induced by SNP was inhibited in Sham but not in 2K-1C rats when the big conductance calcium-activated potassium channel was blocked. However, it remained the same when the other potassium channels were blocked. The protein expression of the SKCa and KATP were not altered in 2K-1C hypertensive rat MRA whereas the expression of KV and BKCa were augmented in MRA from 2K-1C rats. Therefore, the potassium channels play different role on the relaxation induced by SNP and Terpy. The activation of different potassium channels and the protein expression of potassium channels may be differently modulated in arteries from 2K-1C hypertensive rats when compared to normotensive rats.



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