30954752
Salt, salt sensitivity, and the endothelium: a pathway to discovery of molecular mechanisms.
See related article, pp 951–956

This issue of Hypertension contains a report of molecular mechanisms transducing dietary salt intake1 that may have broad clinical relevance. These molecular mechanisms are complex, but to begin to understand this study we have to understand the importance of dietary salt intake and salt sensitivity. This background will be discussed in some detail before discussing the molecular mechanisms.

Although cohort studies have called into question the role of dietary salt intake in causing hypertension,2 cause and effect relationships are most convincing when demonstrated using randomized clinical trials. It would be unethical to perform a randomized clinical trial in which the dietary intake of salt (sodium chloride) is increased for years in humans to observe an increase in blood pressure. However, such an experiment in primates has been performed by Denton et al,3 who studied in Gabon, Africa, 26 chimpanzees. Chimpanzees have a native diet that is vegetarian and is very high in potassium content. The baseline sodium intake in these primates was only 6 mEq/d; in contrast, that of K was 235 mEq/d. Blood pressure was measured in the 26 animals for 1 year. Subsequently, among half the animals, increasing amounts of salt (in increments of 5 g/d sodium) were added to a diet to a steady-state level of 15 g/d. This dietary intake was maintained for 16 months. After this period of dietary supplementation, the diet was switched to baseline and observations made for another 6 months. A dose–response relationship between salt supplementation and blood pressure increment was seen. With 15 g/d sodium supplementation for 67 weeks, the change from baseline in blood pressure was 33/10 mm Hg. In comparison, 5 g/d sodium supplementation for 19 weeks provoked blood pressure change of 12/0 mm Hg. Notably, plasma renin activity was reduced with salt …
36005104
Volume Overload in Dialysis: The Elephant in the Room, No One Can See
interests of the authors. However, considering the totality of the evidence, I am less convinced that this marker is superior to other volume markers. First, there are few head-to-head studies comparing BIA to other established markers of volume. Second, there is no range that defines ‘normal’. Unlike blood pressure (BP) or cholesterol, there is no target that has been established. The normal values are obtained from healthy subjects whose body composition differs substantially from those on dialysis. Extrapolating from healthy subjects to those with ESRD on hemodialysis does not appear scientifically valid. Third, there is no study to my knowledge that demonstrates convincingly that compared to probing dry weight without BIA, BIA-guided dry weight reduction results in improved outcomes. Most data provided to support the use of BIA are associative and observational. A large amount of observational data does not prove causation. We therefore have to be cautious in interpreting these data as ‘strongly indicative of fluid overload’. Nearly all markers of volemia suffer from the same shortcomings. These shortcomings include lack of normative data, and data being largely observational and associative in nature. As an example, several observational studies suggest that B-type natriuretic peptide (BNP), NT-proBNP or other natriuretic peptides are associated with volume state among people with ESRD on dialysis [2–10] . However, only one study has been reported to date that relates the change in BNP to an intervention of probing dry weight [11] . In this study, a direct relationship existed at baseline between BNP and interdialytic ambulatory BP. Since interdialytic ambulatory BP is reVolume overload is the invisible threat to the health of dialysis patients. Currently, Medicare incentivizes the measurement of the dose of dialysis (urea reduction ratio) but has no measure of volume. Perhaps this is because the few who can recognize the epidemic nature of volume excess cannot agree on how to define it. Whereas, some have proposed interdialytic weight gain (IDWG) as a marker of volume, the in-depth review of Hecking et al. [1] quite clearly and importantly makes the distinction that IDWG should not be confused with hypervolemia. One has to wonder how IDWG got confused with dry weight in the first place. It appears that epidemiologists decided to use IDWG as a proxy of dry weight because of its ready availability in large databases. IDWG is a marker that is convenient; it can be measured easily and it can be related to outcomes such as all-cause mortality. This analysis was performed and a relationship emerged between IDWG and all-cause mortality. But establishing a relationship between IDWG and mortality does not establish causality. It could be numerous other factors, measured and unmeasured, associated with IDWG which may be causally related to mortality. Factors such as missing or cutting short dialysis, not taking medications as prescribed, and consuming a diet rich in phosphorus and potassium are some confounding factors that may also be associated with IDWG but may be more plausibly related to mortality. The authors discuss several markers of volume excess. Although several exist, one marker, bioimpedance analysis (BIA), is discussed in great detail. This is understandable given both the academic and intellectual property Published online: July 6, 2013 Nephrology American Journal of
191311
Assessment of iothalamate plasma clearance: duration of study affects quality of GFR.
BACKGROUND AND OBJECTIVES
Measurement of GFR is important for the management of chronic kidney disease (CKD). Although bolus administration of radiocontrast agents is commonly used to measure GFR, the optimal duration of sampling to assess their plasma clearance is unknown. The purpose of this study was to evaluate whether the duration of plasma sampling influences precision and estimation of GFR.


DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS
GFR was measured by sampling plasma 12 times over 5 h in 56 patients with CKD (mean age 64 yr, 98% men, 79% Caucasian, 34% diabetics, estimated GFR 31.8 +/- 14.2 ml/min/1.73 m(2)). In a subset of 12 patients we measured GFR by sampling plasma 17 times over 10 h.


RESULTS
Short sampling intervals considerably overestimated GFR measured using total plasma iothalamate clearance, especially in larger patients. In the higher estimated GFR group (>30 ml/min/1.73 m(2)), the 5-h GFR was 17% higher and 2-h GFR 54% higher compared with the 10-h GFR, which averaged 40.3 ml/min/1.73 m(2). In the lower estimated GFR group (<30 ml/min/1.73 m(2)), the 5-h GFR was 36% higher and 2-h GFR 126% higher compared with the 10-h GFR, which averaged 22.2 ml/min/1.73 m(2). Short sampling duration also reduced the precision of the estimated GFR from 1.67% for 10-h GFR, to 3.48% for 5-h GFR, and to 7.07% for 2-h GFR.


CONCLUSIONS
GFR measured over a longer duration with multiple plasma samples spanning the distribution and elimination phases may improve precision and provide a better measure of renal function.
22176722
Alar web in cleft lip nose deformity: study in adult unilateral clefts.
BACKGROUND
The correction of alar webbing in unilateral cleft lip nose deformity is challenging because of progressive distortions in the alar web region during the period of growth. Alar webbing is a persistent universal deformity in both the primary and secondary cleft lip noses. The purpose of this article is to study the alar web deformity in adult patients with unilateral cleft lip noses.


METHODS
Twenty-five patients aged 13 years and older presenting with unilateral cleft nasal deformity were included. Preoperative and postoperative measurements of the nose, along with detailed intraoperative recording of the deformed anatomy, were done. Preoperative magnetic resonance imaging was also done in selected cases. Transcolumellar open rhinoplasty was performed in all the cases, and nasal septal straightening with centralization was done. Cleft alar base augmentation was done using bone graft to restore symmetry of the nasal tripod. Both the cleft and noncleft alar cartilages were extensively mobilized from the skin and mucosal sides. The overgrown and caudally slumped cleft-side alar cartilage was resected caudally and was then resuspended in a symmetrical position with the noncleft alar cartilage. A midline-strut septal cartilage extension graft was used to restore the tip aesthetics. The skin overlying the alar web was in-rolled after semilunar cartilage resection, and skin excision was also done to restore symmetry with the opposite vestibule. The remaining secondary cleft nasal and lip deformities were corrected depending upon the specific presenting pathologic abnormality.


RESULTS
The cleft alar cartilage was found to be caudally displaced in all the cases. The caudal border of the lateral crus was prolapsing in the cavity of the vestibule on the superomedial aspect and was tenting the skin in the area of the weak triangle, producing the characteristic alar web deformity. In the study group, the maximum width of the cleft alar cartilage at the level of the lateral crus was increased by approximately 4 mm when compared with the noncleft alar cartilage. The before- and after-rhinoplasty surgery results were objectively assessed using a patient, surgeon, and independent observer survey. The cosmetic result of the nasal tip complex was found to be very good and good (90%), satisfactory (5%), and poor (5%) in patients.


CONCLUSIONS
The alar web in unilateral cleft lip nose deformity is the result of caudal overgrowth and migration of the alar cartilage. The caudal edge of the prolapsed lateral crus overhangs the cleft-side nasal aperture on its superomedial aspect, producing this deformity. Satisfactory correction of this deformity should envisage caudal resection and repositioning of the dislocated alar cartilage along with caudal resection of the lateral crus with in-rolling of the skin after resection to achieve symmetric results in unilateral cleft lip rhinoplasty.
11453581
Proinflammatory effects of oxidative stress in chronic kidney disease: role of additional angiotensin II blockade.
Oxidative stress plays an important role in causing progressive chronic kidney disease (CKD). We examined the influence of add-on ANG II receptor blockade administered as losartan (50 mg/day for 1 mo) on oxidative stress and proinflammatory state of the kidney in patients with CKD. All subjects were taking an angiotensin-converting enzyme inhibitor plus other antihypertensive agents. Oxidative stress to lipids and proteins was measured by an HPLC assay for malondialdehyde (MDA) and carbonyl concentration, respectively. Urinary inflammation was measured by monocyte chemotactic protein-1 (MCP-1) excretion rate. The etiology of CKD was type 2 diabetes mellitus in 12 and glomerulonephritis in 4 patients. There was no change in proteinuria or 24-h ambulatory blood pressure (BP) with add-on ANG II receptor blockade with losartan therapy. Before losartan therapy, urinary protein and albumin oxidation were 99 and 71% higher, respectively, compared with in plasma (P < 0.05). There was a 35% reduction in urinary oxidized albumin with add-on losartan therapy (P = 0.036). Urinary and plasma MDA were elevated compared with age-matched controls. Urinary MDA was significantly reduced from 4.75 +/- 3.23 to 3.39 +/- 2.17 micromol/g creatinine with add-on losartan therapy. However, plasma MDA or oxidized proteins did not change in response to additional ANG II blockade. A good correlation was seen between the change in urinary oxidized albumin and MCP-1 levels (r = 0.61, P = 0.012). These data demonstrate that oxidative damage to urinary protein and lipids can be reduced with additional ANG II receptor blockade, independently of reductions in proteinuria or BP. Urinary measurements of markers of oxidative damage to lipids and proteins appear to be more sensitive than plasma measurements in patients with CKD. The significant association of the change in urinary MCP-1 with a reduction in oxidative stress supports the role of the redox state in the kidney with renal fibrosis and progressive kidney damage.
24249726
Regulation of circadian blood pressure: from mice to astronauts.
PURPOSE OF REVIEW
Circadian variation is commonly seen in healthy people; aberration in these biological rhythms is an early sign of disease. Impaired circadian variation of blood pressure (BP) has been shown to be associated with greater target organ damage and with an elevated risk of cardiovascular events independent of the BP load. The purpose of this review is to examine the physiology of circadian BP variation and propose a tripartite model that explains the regulation of circadian BP.


RECENT FINDINGS
The time-keeper in mammals resides centrally in the suprachiasmatic nucleus. Apart from this central clock, molecular clocks exist in most peripheral tissues including vascular tissue and the kidney. These molecular clocks regulate sodium balance, sympathetic function and vascular tone. A physiological model is proposed that integrates our understanding of molecular clocks in mice with the circadian BP variation among humans. The master regulator in this proposed model is the sleep-activity cycle. The equivalents of peripheral clocks are endothelial and adrenergic functions. Thus, in the proposed model, the variation in circadian BP is dependent upon three major factors: physical activity, autonomic function, and sodium sensitivity.


SUMMARY
The integrated consideration of physical activity, autonomic function, and sodium sensitivity appears to explain the physiology of circadian BP variation and the pathophysiology of disrupted BP rhythms in various conditions and disease states. Our understanding of molecular clocks in mice may help to explain the provenance of blunted circadian BP variation even among astronauts.
6949813
An Alternate Method of Classifying Allergic Bronchopulmonary Aspergillosis Based on High-Attenuation Mucus
Background and Aim Allergic bronchopulmonary aspergillosis (ABPA) is classified radiologically based on the findings of central bronchiectasis (CB) and other radiologic features (ORF). However, the long-term clinical significance of these classifications remains unknown. We hypothesized that the immunological activity and outcomes of ABPA could be predicted on HRCT chest finding of high-attenuation mucus (HAM), a marker of inflammatory activity. In this study, we evaluate the severity and clinical outcomes of ABPA with different radiological classifications. Methods Patients were classified based on CT chest findings as: (a) serologic ABPA (ABPA-S) and ABPA-CB; (b) ABPA-S, ABPA-CB, and ABPA-CB-ORF; and, (c) ABPA-S, ABPA-CB and ABPA-CB-HAM. The clinical, spirometric and serological (total and A fumigatus specific IgE levels, eosinophil count) severity of the disease and clinical outcomes in various classifications were analyzed. Results Of the 234 (123 males, 111 females; mean age, 34.1 years) patients, 55 (23.5%) had normal HRCT, 179 (76.5%) had CB, 49 (20.9%) had HAM, and 27 (11.5%) had ORF. All immunological markers were consistently higher in the HAM classification, while in other classifications these findings were inconsistent. On multivariate analysis, the factors predicting frequent relapses were presence of HAM (OR 7.38; 95% CI, 3.21–17.0) and CB (OR 3.93; 95% CI, 1.63–9.48) after adjusting for ORF. Conclusions The classification scheme based on HAM most consistently predicts immunological severity in ABPA. Central bronchiectasis and HAM are independent predictors of recurrent relapses in ABPA. Hence, HAM should be employed in the radiological classification of ABPA.
6343189
Mechanisms of angiotensin converting enzyme inhibitor-induced IOP reduction in normotensive rats.
Angiotensin converting enzyme inhibitors (ACEIs) have been shown to lower intraocular pressure (IOP). Since, the ACEIs cause increased tissue prostaglandin levels, we hypothesized that the mechanisms of ACEI-induced IOP reduction have similarity with those of prostaglandin analogs. The present study investigated the involvement of matrix metalloproteinases (MMPs) and cytokine activity modulation as the underlying mechanisms of ACEI-induced ocular hypotension. The IOP lowering effect of single drop of enalaprilat dehydrate 1% was evaluated in rats pretreated with a broad spectrum MMP inhibitor or a cytokine inhibitor. Effect of angiotensin receptor blocker, losartan potassium 2%, was also studied to evaluate involvement of angiotensin II receptor type 1 (AT1) in IOP lowering effect of ACEI. Topical treatment with single drop of enalaprilat resulted in significant IOP reduction in treated eye with mean peak reduction 20.3% at 3h post-instillation. Treatment with losartan resulted in a peak IOP reduction of 13.3%, which was significantly lower than enalaprilat, indicating involvement of mechanisms in addition to AT1 blockade. Pretreatment with a broad spectrum MMP inhibitor or a cytokine inhibitor significantly attenuated the enalprilat-induced IOP reduction with mean peak IOP reduction of 11.2% and 13.6% respectively. The IOP-lowering effect of enalaprilat seems to be attributed to reduced angiotensin II type 1 receptor stimulation and modulation of MMP and cytokines activities.
22333721
Current concepts in the pathophysiology of glaucoma
Glaucoma, the second leading cause of blindness, is characterized by changes in the optic disc and visual field defects. The elevated intraocular pressure was considered the prime factor responsible for the glaucomatous optic neuropathy involving death of retinal ganglion cells and their axons. Extensive investigations into the pathophysiology of glaucoma now reveal the role of multiple factors in the development of retinal ganglion cell death. A better understanding of the pathophysiological mechanisms involved in the onset and progression of glaucomatous optic neuropathy is crucial in the development of better therapeutic options. This review is an effort to summarize the current concepts in the pathophysiology of glaucoma so that newer therapeutic targets can be recognized. The literature available in the National Medical Library and online Pubmed search engine was used for literature review.
38567456
Is the decrease in LVEDV the mechanism of action of continuous positive airway pressure in diastolic heart failure?
10346616
Mechanisms of cataractogenesis in the presence of magnesium deficiency.
Senile cataract is the most common cause of bilateral blindness and results from the loss of transparency of the lens. Maintenance of the unique tissue architecture of the lens is vital for keeping the lens transparent. Membrane transport mechanisms utilizing several magnesium (Mg)-dependent ATPases, play an important role in maintaining lens homeostasis. Therefore, in Mg-deficiency states, ATPase dysfunctions lead to intracellular depletion of K(+) and accumulation of Na(+) and Ca(2+). High intracellular Ca(2+) causes activation of the enzyme calpain II, which leads to the denaturation of crystallin, the soluble lens protein required for maintaining the transparency of the lens. Mg deficiency also interferes with ATPase functions by causing cellular ATP depletion. Furthermore, Mg deficiency enhances lenticular oxidative stress by increased production of free radicals and depletion of antioxidant defenses. Therefore, Mg supplementation may be of therapeutic value in preventing the onset and progression of cataracts in conditions associated with Mg deficiency.