Angiotensin II attenuates the natriuresis of water immersion in humans

Comparison of Histological Changes in Tissue Specimens Kept in Tap Water, River Water and Seawater for Different Intervals of Time

BACKGROUND

Forensic pathologists find it difficult to ascertain the actual reason for death and the actual mode of death in drowning cases. It is commonly acknowledged that not all people whose dead bodies are found in water perished from drowning. The medico-legal inquiry includes an important component that examines dead bodies collected from the water. The corpse's time in the water continues to be the main concern. This aids in determining the time of death, which is crucial to any medico-legal investigation. The traditional histological analysis of hematoxylin and eosin (H&E)-stained oral soft tissue can be crucial in the assessment of this feature. Hence, this study was done to compare histological changes in the tissue specimens kept in tap water, river water, and seawater for different intervals of time.

MATERIALS AND METHODS

One hundred eighty specimens were obtained from 180 dead bodies and divided randomly into three categories. Category A consisted of 60 specimens submerged in tap water, Category B of 60 specimens submersed in river water, and Category C consisted of 60 specimens submerged in seawater. The specimens underwent routine histological processing and H&E staining. The microscopic evaluation of specimens was carried out at two hours and on the first, second, third, fourth, and fifth days of submersion. Details were recorded regarding the structural changes, cellular changes, connective tissue changes, changes in the basement membrane, and intensity of H&E staining. Once the process of routine histological processing and H&E staining was completed for each study specimen, an evaluation of microscopic changes in the tissue was made.

RESULTS

The present study revealed that seawater preserved tissue best and for a longer period than river water and tap water. River water preserved tissue better than tap water. In pathologic tissue, details were preserved for much longer. It was noted that in squamous cell carcinoma, connective tissue was destroyed earlier than epithelium, in contrast to normal tissue where epithelium was destroyed before connective tissue.

CONCLUSION

This study indicates that the medium of submersion in drowning victims affects the histopathological features. The time of death is an important aspect of forensic investigation. Considering this, all cases of drowning should be very carefully evaluated, and the medium taken into consideration while determining the time of death, as tissue degrades faster in freshwater than in seawater.

Statin Use Improves Cardiometabolic Protection Promoted By Physical Training in an Aquatic Environment: A Randomized Clinical Trial

BACKGROUND

Statin use is highlighted as the most commonly utilized therapy for the treatment of dyslipidemias and can be considered as the most efficient pharmacological intervention for low-density lipoprotein (LDL) reduction. On the other hand, physical training can be considered an efficient and safe non-pharmacological strategy to promote improvements in lipid profile. However, the influence of statins on lipid adaptations arising from water-based training in populations with dyslipidemia is not known.

OBJECTIVES

To analyze the influence of simvastatin use on lipid adaptations arising from water-based aerobics and resistance training in elderly women with dyslipidemia.

METHODS

Sixty-nine elderly (66.13 ± 5.13 years), sedentary, and dyslipidemic women, both non-users and users of simvastatin (20 mg and 40 mg), were randomized into the following 3 groups: water-based aerobic training (WA), water-based resistance training (WR), and control group (CG). Total duration of interventions, for all experimental groups consisted of 10 weeks, with 2 weekly sessions. Biochemical analyses were performed before the beginning of the interventions and repeated after the end of the trial. Generalized estimating equations were used to compare these data, setting α = 0.05.

RESULTS

In intention-to-treat analysis, the medicated participants obtained a greater magnitude of decrease in total cholesterol (TC) (-3.41 to -25.89 mg.dl-1; p = 0.038), LDL (-5.58 to -25.18 mg.dl-1; p = 0.007) and TC/HDL ratio (-0.37 to -0.61; p = 0.022) when compared to the non-medicated participants, and this decrease was statistically significant only in the WR group.

CONCLUSIONS

Statin use enhances the adaptations promoted by water-based physical training in CT, LDL levels, and CT/HDL ratio, and it is more pronounced after WR.

Anaerobic Threshold in a Water-Based Exercise: Agreement Between Heart Rate Deflection Point and Lactate Threshold Methods

ABSTRACT

Alberton, CL, Andrade, LS, Pinheiro, RB, and Pinto, SS. Anaerobic threshold in a water-based exercise: agreement between heart rate deflection point and lactate threshold methods. J Strength Cond Res 35(9): 2472-2478, 2021-The purpose of this study was to compare and assess the agreement of the heart rate (HR) and rating of perceived exertion (RPE) corresponding to the anaerobic threshold (AT) between HR deflection point (HRDP) and lactate threshold (LT) methods during a water-based exercise in young men. Sixteen young men (24 ± 6 years) performed the experimental protocol, which comprised the performance of a maximal incremental test during the water-based stationary running exercise. The initial cadence corresponded to 90 b·min-1, with 10 b·min-1 increases every 3 minutes up to exhaustion. Heart rate was monitored every 30 seconds while blood lactate concentrations and RPE were measured at the end of each 3-minute bout. Anaerobic threshold was identified by HRDP and LT methods by experienced physiologists. Paired Student's t-test, Bland-Altman analysis, and Pearson correlation were used for data analysis (α = 0.05). As results, there was agreement between HRDP and LT methods for HR, while RPE presented significant higher values for the HRDP method, resulting in an absence of acceptable agreement between methods. In addition, strong relationships (p ≤ 0.001) were verified between methods of AT determination for HR (r = 0.786) and RPE (r = 0.916). Therefore, based on the agreement between HRDP and LT methods, the HR determined by HRDP may be a valid parameter used for the intensity prescription of water-based stationary running exercise in young men during water aerobics programs and may be considered more reliable than RPE.

The beneficial effects of a water-based aerobic exercise session on the blood lipids of women with dyslipidemia are independent of their training status

OBJECTIVES

To evaluate the acute effects of a session of water-based aerobic exercise on the blood lipid levels of women with dyslipidemia and to compare these results according to their training status.

METHOD

Fourteen premenopausal women with dyslipidemia, aged 40-50 years, participated in two water-based aerobic exercise sessions, the first when they were generally sedentary and the second after they were trained with a water-based aerobic training program for 12 weeks. Both experimental sessions were performed using the same protocol, lasted 45 min, and incorporated an interval method, alternating 3 min at a rating of perceived exertion (RPE) of 13 and 2 min at an RPE of 9. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and lipoprotein lipase enzyme (LPL) were obtained through venous blood collection before and immediately after each session. A generalized estimating equation method and Bonferroni tests were conducted (with time and training status as factors) for statistical analyses.

RESULTS

At enrollment, the mean age of the participants was 46.57 years (95% confidence interval [CI] 44.81-48.34). The statistical analyses showed a significant time effect for all variables (TC: p=0.008; TG: p=0.012; HDL: p<0.001; LPL: p<0.001) except for LDL (p=0.307). However, the training status effect was not significant for any variable (TC: p=0.527; TG: p=0.899; HDL: p=0.938; LDL: p=0.522; LPL: p=0.737). These results indicate that the TC and TG levels reduced and the HDL and LPL concentrations increased from pre- to post-session in similar magnitudes in both sedentary and trained women.

CONCLUSIONS

A single water-based aerobic exercise session is sufficient and effective to beneficially modify the lipid profile of women with dyslipidemia, regardless of their training status.

Water-Based Aerobic and Resistance Training as a Treatment to Improve the Lipid Profile of Women With Dyslipidemia: A Randomized Controlled Trial

Background: Regular exercise is recommended for the treatment of dyslipidemia. The aquatic environment presents some beneficial characteristics for patients suffering from dyslipidemia. However, it is unknown which modality promotes better results. This study aims to compare the effects of water-based aerobic training (WA) and water-based resistance training (WR) on lipid profile of dyslipidemic elderly women. Methods: Sixty-nine dyslipidemic elderly women participated in this 3-arm randomized controlled clinical trial with groups in parallel. The interventions were WA, WR, and control group, with 2 weekly sessions for 10 weeks. Total cholesterol (TC), triglycerides, low-density lipoprotein, high-density lipoprotein (HDL) levels, and TC/HDL ratio, were determined before and after interventions. Results: Intention-to-treat analysis showed that WA and WR participants obtained similar decreases in TC (-10.0% and -9.6%, respectively), triglycerides (-13.4% and -15.7%, respectively), low-density lipoprotein (-16.1% and -16.9%, respectively), TC/HDL (-16.9% and -23.4%, respectively) and increases in HDL (7.6% and 16.9%, respectively). The control group maintained their TC and low-density lipoprotein levels unchanged, whereas triglycerides and TC/HDL were increased (3.6% and 11.3%, respectively), and HDL decreases 4.8%. Conclusions: WA and WR improve similarly the lipid profile of dyslipidemic elderly women, representing interesting nonpharmacological tools in the treatment of dyslipidemia.

Human Physiology in an Aquatic Environment

Water covers over 70% of the earth, has varying depths and temperatures and contains much of the earth's resources. Head-out water immersion (HOWI) or submersion at various depths (diving) in water of thermoneutral (TN) temperature elicits profound cardiorespiratory, endocrine, and renal responses. The translocation of blood into the thorax and elevation of plasma volume by autotransfusion of fluid from cells to the vascular compartment lead to increased cardiac stroke volume and output and there is a hyperperfusion of some tissues. Pulmonary artery and capillary hydrostatic pressures increase causing a decline in vital capacity with the potential for pulmonary edema. Atrial stretch and increased arterial pressure cause reflex autonomic responses which result in endocrine changes that return plasma volume and arterial pressure to preimmersion levels. Plasma volume is regulated via a reflex diuresis and natriuresis. Hydrostatic pressure also leads to elastic loading of the chest, increasing work of breathing, energy cost, and thus blood flow to respiratory muscles. Decreases in water temperature in HOWI do not affect the cardiac output compared to TN; however, they influence heart rate and the distribution of muscle and fat blood flow. The reduced muscle blood flow results in a reduced maximal oxygen consumption. The properties of water determine the mechanical load and the physiological responses during exercise in water (e.g. swimming and water based activities). Increased hydrostatic pressure caused by submersion does not affect stroke volume; however, progressive bradycardia decreases cardiac output. During submersion, compressed gas must be breathed which introduces the potential for oxygen toxicity, narcosis due to nitrogen, and tissue and vascular gas bubbles during decompression and after may cause pain in joints and the nervous system.

Mechanism of 1-deamino-arginine vasotocin induced natriuresis in rats

1-Deamino-arginine vasotocin (1dAVT) induced diuresis and a considerable increase in urinary sodium excretion in female Wistar rats. Sodium fractional excretion rose up to 19.3 ± 1.1%. An increase in urine flow rate after 1dAVT (0.5 nmol/kg body-weight [bw]) injection was accompanied by a significant rise of the solute-free water reabsorption. The 1dAVT-induced natriuresis was as high as natriuresis produced by injection of a maximal dose of furosemide (10mg/kg bw). V(1)-receptor antagonists (ОРС-21268, [β-mercapto-β,β-cyclopentamethylenepropionyl(1),O-Me-Tyr(2),Arg(8)]-vasopressin) blocked the increase in urinary sodium excretion after the 1dAVT injection. The 1dAVT-induced natriuresis was strongly correlated with an increase in the urinary cGMP and prostaglandin E(2) excretion. The natriuretic effect of 1dAVT did not depend on the formation of nitric oxide (NO) or atrial natriuretic peptide of which concentration in the rat blood serum remained stable. The above results indicate that the 1dAVT has unique effects on rat kidney compared to all other known diuretics - it induces extremely high natriuresis and stimulates solute-free water reabsorption. Mechanism of the natriuretic effect of 1dAVT includes decrease in tubular sodium reabsorption due to activation of V(1)-like receptors and formation of cGMP and PGЕ(2).

Forensic investigation of submersion deaths

CONTEXT

The diagnosis of the cause and the establishment of the manner of death in submersion cases are routine challenge for forensic pathologists as it presents considerable diagnostic difficulties.

OBJECTIVE

To concisely review the main questions during a submersion death investigation and to give the respective documented answers.

DATA SOURCES

The search strategy included a literature search of PubMed, Medline and Google Scholar databases, as well as a review of the cited references by the identified studies and a hand search of relevant textbooks and reference works.

CONCLUSIONS

A complete autopsy, histopathological examination and full toxicological screening are important to determine whether death indeed followed submersion in the water, or to see whether any natural disease or substance use have contributed or caused death. In ambiguous situations, the co-estimation of circumstantial evidence may be of invaluable importance toward the conclusion concerning the cause and the manner of death. The thorough forensic investigation of the submersion deaths not only serves the justice administration, but it also presents considerable benefits for the public health.

Effects of truncated angiotensins in humans after double blockade of the renin system

Angiotensins different from ANG II exhibit biological activities, possibly mediated via receptors other than ANG II receptors. We studied the effects of 3-h infusions of ANG III, ANG-(1-7), and ANG IV in doses equimolar to physiological amounts of ANG II (3 pmol. kg-1. min-1), in six men on low-sodium diet (30 mmol/day). The subjects were acutely pretreated with canrenoate and captopril to inhibit aldosterone actions and ANG II synthesis, respectively. ANG II infusion increased plasma angiotensin immunoreactivity to 53 +/- 6 pg/ml (+490%), plasma aldosterone to 342 +/- 38 pg/ml (+109%), and blood pressure by 27%. Glomerular filtration rate decreased by 16%. Concomitantly, clearance of endogenous lithium fell by 66%, and fractional proximal reabsorption of sodium increased from 77 to 92%; absolute proximal reabsorption rate of sodium remained constant. ANG II decreased sodium excretion by 70%, potassium excretion by 50%, and urine flow by 80%, whereas urine osmolality increased. ANG III also increased plasma aldosterone markedly (+45%), however, without measurable changes in angiotensin immunoreactivity, glomerular filtration rate, or renal excretion rates. During vehicle infusion, plasma renin activity decreased markedly ( approximately 700 to approximately 200 mIU/l); only ANG II enhanced this decrease. ANG-(1-7) and ANG IV did not change any of the measured variables persistently. It is concluded that 1) ANG III and ANG IV are cleared much faster from plasma than ANG II, 2) ANG II causes hypofiltration, urinary concentration, and sodium and potassium retention at constant plasma concentrations of vasopressin and atrial natriuretic peptide, and 3) a very small increase in the concentration of ANG III, undetectable by usual techniques, may increase aldosterone secretion substantially.

Mechanisms of acute natriuresis in normal humans on low sodium diet

This study evaluates the relative importance of several mechanisms possibly involved in the natriuresis elicited by slow sodium loading, i.e. the renin-angiotensin-aldosterone system (RAAS), mean arterial blood pressure (MAP), glomerular filtration rate (GFR), atrial natriuretic peptide (ANP), oxytocin and nitric oxide (NO). Eight seated subjects on standardised sodium intake (30 mmol NaCl day(-1)) received isotonic saline intravenously (NaLoading: 20 micromol Na(+) kg(-1) min(-1) or approximately 11 ml min(-1) for 240 min). NaLoading did not change MAP or GFR (by clearance of (51)Cr-EDTA). Significant natriuresis occurred within 1 h (from 9 +/- 3 to 13 +/- 2 micromol min(-1)). A 6-fold increase was found during the last hour of infusion as plasma renin activity, angiotensin II (ANGII) and aldosterone decreased markedly. Sodium excretion continued to increase after NaLoading. During NaLoading, plasma renin activity and ANGII were linearly related (R = 0.997) as were ANGII and aldosterone (R = 0.999). The slopes were 0.40 pM ANGII (mi.u. renin activity)(-1) and 22 pM aldosterone (pM ANGII)(-1). Plasma ANP and oxytocin remained unchanged, as did the urinary excretion rates of cGMP and NO metabolites (NO(x)). In conclusion, sodium excretion may increase 7-fold without changes in MAP, GFR, plasma ANP, plasma oxytocin, and cGMP- and NO(x) excretion, but concomitant with marked decreases in circulating RAAS components. The immediate renal response to sodium excess appears to be fading of ANGII-mediated tubular sodium reabsorption. Subsequently the decrease in aldosterone may become important.

Role of cardiac-renal neural reflex in regulating sodium excretion during water immersion in conscious dogs

The present study was undertaken to determine the role of cardiopulmonary mechanoreceptors in inducing the sustained reduction of renal sympathetic nerve activity (RSNA) and concomitant changes in sodium excretion occurring during water immersion (WI) in intact dogs. Seven cardiac-denervated dogs were chronically instrumented for measuring RSNA, systemic arterial (P(a)), central venous (P(cv)) and left atrial pressures (P(la)). WI initially decreased RSNA in cardiac denervated dogs by 10.0 +/- 5.5 %; thereafter the RSNA fell to a nadir of 18.5 +/- 5.6 % (P < 0.05) at 40-80 min of WI and then returned toward the pre-immersion level. Renal sodium excretion increased significantly by 211 +/- 69 % (P < 0.05) only during the first 20-40 min of WI. WI increased P(a), P(cv) and P(la) in a step manner from 94 +/- 3 to 108 +/- 3 mmHg (P < 0.05), from 1.4 +/- 0.5 to 12.3 +/- 1.0 mmHg (P < 0.05) and from 4.9 +/- 0.6 to 15.4 +/- 1.2 mmHg (P < 0.05), respectively. These responses in RSNA and sodium excretion to WI in the cardiac-denervated dogs were significantly (P < 0.05) attenuated compared with those in a previous group of intact dogs. These data suggest that the attenuated responses of neural and excretory response to WI observed in cardiac-denervated dogs can be attributed to an interruption of afferent input originating from the cardiopulmonary mechanoreceptors to the central nervous system.

Diuretic response to acute hypertension is blunted during angiotensin II clamp

Acute hypertension inhibits proximal tubule (PT) fluid reabsorption. The resultant increase in end proximal flow rate provides the error signal to mediate tubuloglomerular feedback autoregulation of renal blood flow and glomerular filtration rate and suppresses renal renin secretion. To test whether the suppression of the renin-angiotensin system during acute hypertension affects the magnitude of the inhibition of PT fluid and sodium reabsorption, plasma ANG II levels were clamped by infusion of the angiotensin-converting enzyme (ACE) inhibitor captopril (12 microg/min) and ANG II after pretreatment with the bradykinin B(2) receptor blocker HOE-140 (100 microg/kg bolus). Because ACE also degrades bradykinin, HOE-140 was included to block effect of accumulating vasodilatory bradykinins during captopril infusion. HOE-140 increased the sensitivity of arterial blood pressure to ANG II: after captopril infusion without HOE-140, 20 ng x kg(-1) x min(-1) ANG II had no pressor effect, whereas with HOE-140, 20 ng x kg(-1) x min(-1) ANG II increased blood pressure from 104 +/- 4 to 140 +/- 6 mmHg. ANG II infused at 2 ng x kg(-1) x min(-1) had no pressor effect after captopril and HOE-140 infusion ("ANG II clamp"). When blood pressure was acutely increased 50-60 mmHg by arterial constriction without ANG II clamp, urine output and endogenous lithium clearance increased 4.0- and 6.7-fold, respectively. With ANG II clamp, the effects of acute hypertension were reduced 50%: urine output and endogenous lithium clearance increased two- and threefold, respectively. We conclude that HOE-140, an inhibitor of the B(2) receptor, potentiates the sensitivity of arterial pressure to ANG II and that clamping systemic ANG II levels during acute hypertension blunts the magnitude of the pressure diuretic response.