Hypertension In Renal Patients Research Articles

Prevalence of hypertension in renal disease.

Hypertension (HTN) is very frequent in patients with renal disease and its prevalence increases as renal failure progresses. We studied the prevalence of HTN in 1921 patients with different nephropathies. Patients on dialysis and renal transplant patients were not included in the study. HTN was defined as SBP>140 and/or DBP>90 mmHg, or requiring antihypertensive therapy. The prevalence of HTN in the total group of patients with renal diseases was 60.5%, but this prevalence varied widely depending upon the type of underlying nephropathy. The prevalence of HTN was practically universal in patients with renal vascular disease (93%) and in patients with established diabetic nephropathy (87%), and 74% of the patients with polycystic kidney disease, 63% of the patients with chronic pyelonephritis and 54% of the patients diagnosed with glomerulonephritis were hypertensive. The prevalence of HTN in patients with renal insufficiency (80%) is significantly higher than that in patients without renal insufficiency (43% P<0.001). In a multiple logistic regression analysis, the independent risk factors defining HTN in renal patients were: renal failure, age, the presence of diabetes, hypertriglyceridaemia and proteinuria. Antihypertensive treatment consisted of diet alone in 4% of the patients, one drug in 45%, two drugs in 36%, three medications in 13% and more than three drugs in 2.5%. The angiotensin-converting enzyme (ACE) inhibitors were the most frequently prescribed drug (39% of the patients treated in monotherapy) followed by calcium channel blockers (27%), diuretics (18%) and beta-blockers (9%). The most common combined therapy was a diuretic plus an ACE inhibitor. The percentage of patients with BP controlled according to current recommendations for renal patients (BP<130/85) was very low; SBP in only 49% and DBP in 24%. Control of both was only achieved in 10% of the patients. There is a high prevalence of HTN in renal patients, which depends on the type of nephropathy and the degree of renal failure. Other independent risk factors for HTN in patients with renal disease are: advanced age, the presence of diabetes, hypertriglyceridaemia and the severity of proteinuria. BP control in renal patients is quite poor and should be improved to reduce progression of the renal disease.

The effect of sodium restriction and weight reduction on blood pressure of patients with hypertension and chronic renal disease

Objective: To examine the blood pressure (BP) effect of sodium intake and weight changes in hypertensive patients with moderate to advanced chronic renal diseases. Design: Subgroup analyses comparing urine, sodium, weight, and BP changes by lifestyle modification (sodium, weight, sodium and weight, or none). Setting: 15 US clinical centers Patients: 724 hypertensive patients with chronic renal disease used in the Modification of Diet in Renal Disease (MDRD) Study Group. Interventions: Primary MDRD interventions were protein and phosphorus reductions in the diet and hypertension treatment with antihypertensive medications. Secondary interventions included lifestyle modifications. Main outcome measures: BP changes during 18 months of follow-up. Results: In this study, 51.2% of patients were prescribed sodium or weight modifications: sodium or sodium plus weight loss (31.2%) and weight alone (20.0%). After 18 months, sodium reductions averaged 4.3 mmol/L in the usual mean arterial pressure (MAP) group and 20.7 mmol/L in the low MAP group. Weight reductions averaged 2.0 kg in the usual MAP group and 1.4 kg in the low MAP group. BP decreased more in low MAP patients advised to reduce sodium or weight (−4.5 to −5.7 mm Hg; P = .0002), and patients on both weight and sodium modifications showed the largest decrease. Multiple regression analyses revealed significant association between weight change and BP in low MAP patients. Cautious interpretation is recommended because these were subgroup analyses and participants were not randomly assigned to lifestyle modifications. Conclusion: Planned weight loss and modest sodium reductions were observed in hypertensive MDRD Study participants on concurrent dietary protein and phosphorus and antihypertensive medication interventions. Sodium or weight benefits were greater in hypertensives randomized to low MAP and low protein goals. Even modest weight loss appeared beneficial for BP management. Weight loss benefits to blood pressure management would be important to confirm in future randomized studies of hypertensive renal patients.

Intracellular magnesium content in hypertension

A method to determine total Mg2+ content in lymphocytes was developed, offering advantages for routine measurements as compared to fluorescence methods. Intracellular Mg2+ measurements were performed in lymphocytes of 16 normotensive, 20 essential hypertensive, 15 renal hypertensive patients (patients with a chronic glomerulonephritis), and 10 normotensive, renal insufficient patients. Mg2+ content was referred to lymphocytic protein, which was determined according to Bradford's method. Mg2+ measurements were performed by atomic absorption spectroscopy using an electrothermal atomic absorption spectroscope. The results show that in patients with essential hypertension, intralymphocytic Mg2+ content is significantly lower (0.07 ± 0.04 mmol/g lymphocytic protein, mean ± SD) compared with controls (0.11 ± 0.03 mmol/g lymphocytic protein, mean ± SD,p <0.05). In renal hypertensive patients, intracellular Mg2+ concentrations are significantly increased compared with normotensive or essential hypertensive patients (0.35 ± 0.10 mmol/g lymphocytic protein, mean ± SD,p <0.05). In the normotensive renal insufficient group, intracellular Mg2+ concentrations were measured (0.37 ± 0.05 mmol/g lymphocytic protein, mean ± SD being significantly increased compared to the normotensive or hypertensive group (p <0.05). There was no significant difference between the renal insufficient group with and without arterial hypertension. In plasma Mg2+ concentrations there was no significant difference in the four groups of patients. Furthermore, this method also seems suitable for routine measurements of cellular Mg2+ concentrations in even larger groups of patients.

An anatomical and physiological model of the renal parenchyma-model development and parametric identification

Renal function is often characterized by the activity/time curves obtained by imaging the aorta and kidney. Non-parametric deconvolution of the activity/time curves is clinically useful as a diagnostic tool in determining renal transit times. Typically non-parametric deconvolution is performed using a technique that does not require a priori information, e.g. matrix-based and Fourier-transform methods. Using data filtering and conservation of mass constraints, non-parametric deconvolution continues to exhibit noise in the deconvolved curves. This noise hampers the identification of renal transit times. Given the shortcomings of non-parametric deconvolution, a parametric model of the renal response has been developed. The authors' model is shown to be anatomically and physiologically plausible. Here, the parametric model structure is used, in conjunction with experimental data, to estimate renal physiological parameters. These parameters include the filtration fraction, renal blood transit time and urine transit times. The model parameters are then related to the minimum transit time (MinTT), mean transit time (MTT), glomerular filtration rate (GFR) and parenchymal transit time index (PTTI). As deconvolution techniques often produce negative artifacts, Fine et al. (1993) developed a technique to determine an aorta background to minimize this effect. Here this work is extended to determine a reasonable renal background from aorta activity/time curves. Non-parametric deconvolution is used to provide initial estimates of model parameters. The model is then fitted to twelve healthy background-corrected kidneys by an iterative parameter-estimation technique. The normal values correspond to those reported in the literature. These normal values are then used to identify renal arterial stenosis in two renal hypertensive patients. The results suggest that parametric identification, based on a renal-retention-function model, may provide additional anatomical and physiological information that is not provided by conventional non-parametric methods.

Effects of manidipine hydrochloride on renal function in renal parenchymal hypertensive patients

The incidence of renal parenchymal hypertension is highest in patients with secondary hypertension. It is important to prevent the progression of renal dysfunction by appropriate treatment, especially by means of antihypertensive drugs. Calcium channel blockers are considered to have the advantage as antihypertensive drugs of maintaining the renal blood flow, even though the perfusion pressure may be decreased. However, these drugs can involve the risk of deteriorating the glomerular function due to hyperfiltration. To investigate whether calcium channel blockers can prevent the deterioration of renal function in renal parenchymal hypertensive patients, we administered manidipine hydrochloride (20 mg, once a day, 24 weeks) to 16 outpatients and evaluated its effects on blood pressure and renal function. The following results were obtained. (1) The systolic and diastolic pressure decreased from 2 and 4 weeks after administration, respectively. A stable antihypertensive effect appeared thereafter and no change was observed in the pulse rate. (2) The renal vascular resistance tended to decrease slightly. The glomerular filtration rate and renal blood flow did not change in spite of the decreased perfusion pressure. (3) No changes were seen in urinary protein, endocrine factors and cardiac function. (4) In some of the cases with decreased GFR (< 70ml/min), the drug could not prevent deterioration of the renal function and did not produce an antihypertensive effect.

Circadian Blood Pressure Changes in Patients with Chronic Renal Insufficiency: A Prospective Study

Circadian blood pressure (BP) rhythm was prospectively studied by ambulatory 24-h monitoring in normotensive (n = 27) and hypertensive (n = 41) patients with stable progression of chronic renal insufficiency, and in matched control groups (healthy subjects: n = 28 and patients with essential hypertension: n = 47) without renal disease. The follow-up period lasted 24 months. The renal patients showed a disturbance in the 24-h profile of BP, with significantly blunted nocturnal pressure reduction as compared with the respective control groups (p < 0.01 and p < 0.001, respectively). In addition to the rearrangement of circadian rhythm, the normotensive and hypertensive renal patients displayed a wider distribution of systolic and diastolic BP values and a greater nocturnal variability. Among the normotensive and hypertensive patients with chronic renal insufficiency, a significant correlation was found between the decline in creatinine clearance over the 24-month period and the average nighttime diastolic BP (r = 0.526; p < 0.01 and r = 0.613; p = 0.001, respectively) and nocturnal diastolic fall (r = 0.612; p < 0.001 and r = 0.496; p < 0.01, respectively). These data offer support for the view that renal normotensive patients are exposed to a relative hypertension at nighttime and that renal hypertensive subjects can be underestimated in their hypertensive status if the measurement of BP is confined to daytime. In both groups, nocturnal BP overload can accelerate the progression rate of renal insufficiency.

Modulation of platelet Ca2+ homeostasis by hypertensive plasma factor(s) derived from patients with early-stage renal disease.

To determine whether blood-borne factors in hypertension accompanying early-stage kidney disease might be responsible for altered cellular calcium homeostasis, we measured changes in cytosolic calcium before and after incubating platelets in plasma ultrafiltrates from normotensive and hypertensive renal patients. With the use of the chelating agent quin 2, we found the free-calcium concentrations in platelets to be higher in the hypertensive than in the normotensive group. When both groups of participants were combined, a direct correlation was found between arterial pressure and cytosolic calcium. The cytosolic calcium concentration in platelets of normotensive renal patients increased after incubation with plasma from patients with untreated renal hypertension, but it was unchanged after incubation with plasma from normotensive subjects. These data indicate that the total cell burden of calcium is increased in platelets of hypertensive patients with early-stage renal disease, and that plasma from these patients contains a substance that is capable of increasing the cytosolic calcium concentration in platelets. If the plasma factor (or factors) acts not only on platelets, but also on vascular smooth muscle cells, it may contribute to the increased peripheral vascular resistance associated with hypertension of renal origin.

Platelet cytosolic free calcium concentration in hypertension associated with early stage kidney disease.

Chronic hypertension accompanying early stage kidney disease is characterized by increased vascular resistance, but the underlying processes responsible for the enhanced vascular tone are unclear. We studied free calcium levels in blood platelets with the fluorescent dye quin-2. Platelets have many features in common with vascular smooth muscle cells. The cytosolic calcium concentration in platelets was elevated in 27 renal hypertensive patients, who were compared with 12 normotensive subjects (P less than 0.001). There was a close correlation between the free calcium level and mean blood pressure (r = 0.88, P less than 0.001). Short-term antihypertensive treatment with a calcium entry blocker or a diuretic resulted in a significant reduction in cytosolic calcium (P less than 0.05), and this correlated with the fall in blood pressure (r = 0.95, P less than 0.001). These data suggest an integrative contributory role of calcium in the pathophysiology of hypertension accompanying early stage kidney disease.

Effects of converting enzyme inhibition on split renal function in renovascular hypertension.

The effects of captopril on effective renal plasma flow and glomerular filtration rate were studied using a noninvasive radioisotopic method on individual kidneys in eight patients with renovascular hypertension and 12 patients with essential hypertension with various renin levels. Four patients with renovascular hypertension had unilateral while three had bilateral renal artery stenosis. The effective renal plasma flow and glomerular filtration rate were determined by using 131I-iodohippurate sodium and 99mTc-diethylenetriamine pentaacetic acid, respectively. Glomerular filtration rate and effective renal plasma flow were significantly reduced in the stenotic kidneys of patients with renovascular hypertension compared with values in nonstenotic kidneys (p less than 0.01). Treatment with captopril, 37.5 to 75 mg/day for 1 to 48 weeks, further reduced the glomerular filtration rate only in stenotic kidneys, and effective renal plasma flow increased in both kidney types. In two of the three renal hypertensive patients with bilateral renal artery stenosis, captopril produced a reversible azotemia that was unrelated to the fall in blood pressure, as evidenced by the lack of azotemia seen after a moderate blood pressure reduction induced by other antihypertensive medications. These results indicate that endogenous angiotensin II is essential in maintaining the glomerular filtration rate in stenotic kidneys and suggest that a reduction in glomerular filtration rate during captopril administration could indicate the presence of renal artery stenosis.

Urinary kallikrein and prostaglandin E2 excretion before and after operation in adrenal and renal hypertensive patients

Urinary kallikrein and prostaglandin E<SUB>2</SUB> excretion before and after operation in adrenal and renal hypertensive patients

Sodium-lithium exchange and sodium-potassium cotransport in human erythrocytes. Part 2: A simple uptake test applied to normotensive and essential hypertensive individuals.

The sodium-lithium (Na+-Li+) exchange and sodium-potassium (Na+-K+) cotransport activities were assessed on erythrocytes of 38 normotensive individuals, 18 patients with well-established essential hypertension, and five renal hypertensive patients, by means of an uptake assay method. With both transport systems, no significant differences in mean values and variance were observed among the three groups. Four of six low-renin essential hypertensive patients exhibited some of the lowest exchange and cotransport rates obtained among all individuals examined. The activity of both transport systems was slightly lower in women than in men.

Treatment of hypertension in dialysis and essential hypertension patients with nifedipine.

The immediate antihypertensive effect of 10 mg nifedipine sublingually (nifedipine test), was measured in 19 chronic renal failure hypertensive patients on dialysis and 34 essential hypertensive patients with normal kidney function. The blood pressure decreased significantly in both groups. The minimal values were observed between 30 and 60 minutes after the sublingual administration of nifedipine. The blood pressure decreased from 178 +/- 3.3/104.0 +/- 3.9 to 136.0 +/- 4.7/87.5 +/- 5.1 mm Hg (p less than 0.001) in dialysis patients and from 176.8 +/- 4.5/107.1 +/- 2.4 to 133.0 +/- 3.0/81.7 +/- 2.2 mm Hg in essential hypertension patients (p less than 0.001). The decrease in blood pressure during the test had a significant positive correlation with the pre-test values. Thirteen hypertensive patients on dialysis and 20 essential hypertensive patients completed 2 weeks of daily oral nifedipine therapy, with a dose of 30 to 40 mg per day. The mean blood pressure at the end of the 2 weeks of treatment decreased from 179.5 +/- 4.5/108.5 +/- 5.3 mm Hg to 154.4 +/- 6.3/82.3 +/- 2.6 mm Hg (p less than 0.001) in dialysis patients, and from 176.8 +/- 5.8/110.3 +/- 2.9 to 151.3 +/- 5.3/93.5 +/- 2.6 mm Hg (p less than 0.001) in essential hypertension patients. The present results reveal that nifedipine has a powerful immediate as well as a long-term antihypertensive action in dialysis patients with high blood pressure. This effect is similar to that obtained in essential hypertensive patients.

Cerebrospinal fluid and plasma dopamine-beta-hydroxylase activity in human hypertension.

Cerebrospinal fluid (CSF) and plasma dopamine-beta-hydroxylase (DBH) activity was measured in 22 normotensive (NT), 31 essential hypertensive (EH), and 11 renal hypertensive (RH) patients. Although no differences were observed in their plasma DBH, the mean CSF-DBH activity and specific activity of EH were significantly lower than those of NT and RH patients. Very low CSF-DBH (less than 0.15 units/ml of CFS or less than 0.5 units/mg of CSF protein) was found only in EH (26% of EH). Of the 31 EH patients, 19(60%) had CSF-DHB activities lower than 0.5 units/ml, whereas only 5 of 22 NT (23%) and no RH fell within this range. Nevertheless, 20% of EH, 55% of NT, and 40% of RH patients had CSF-DBH activities above the mean value for NT (less than 0.9 units/ml). NT subjects with very low plasma DBH (less than 50 units/ml) had CSF-DBH activities that fell within normal range. With the exception of these subjects, the specific activity of CSF-DBH was always lower than that of the plasma enzyme. The concentration of albumin, alpha 1, beta, and gamma globulins was measured in plasma and CSF obtained from the last five NT, four EH, and two RH patients. A positive linear relationship was obtained when the log of the plasma/CSF concentration ratio for these proteins was plotted against their molecular weight. Similar slopes and intercepts were obtained for these patients, suggesting that no major differences seem to exist in their blood-brain-barrier permeability to proteins. The results suggest that measurements of CSF-DBH could be of help in the differential diagnosis of human hypertension and in the neurochemical characterization of EH. If CSF-DBH reflects central noradrenergic activity, its reduction might indicate the existence of a central catecholaminergic defect in a subgroup of EH patients.

Haemodynamic changes during acute emotional stress in man with special reference to the capacitance vessels

It has been established that in acute emotional stress (for example mental arithmetics) the raised cardiac output is shifted from the viscera and skin to the skeletal muscle and myocardium. The present study was undertaken to fill the gap in information about the behaviour of the capacitance vascular bed during emotional stress. The investigation was carried out in 6 healthy normotensives, 9 normotensive patients with chronic renal disease, 19 hypertensive renal patients and 12 essential hypertensives. As there was no statistically significant difference in their response to emotional stress they were eventually analyzed as one group (46 subjects). The emotional stress caused a rise of mean blood pressure by 19 mm Hg, the heart rate by 16/min and the cardiac index by 1.42 ml/min/m2. Total peripheral vascular resistance did not change significantly. Central and peripheral venous pressure rose by 2 and 2.5 mm Hg. The forearm muscle blood flow increased from 4.0 to 7.8 ml/min/100 g and the forearm vascular resistance decreased by 10.8 dyn·cm−5·s·105. It was found that this rise in forearm muscle blood flow was not accompanied by any significant rise in the forearm blood volume. The venous distensibility had a tendency to decrease with the exception of some hypertensive subjects who had the lowest venous distensibility at rest. These changes are suggestive of a stiffening of the peripheral veins, preventing pooling of the additional blood supplying the muscles during emotional stress in the extremities. This supports the conclusion that the veins play an active part in the cardiovascular response to emotional stress.

Plasma renin activity and aldosterone secretion rate in hypertension. The distinction between primary and secondary hyperaldosteronism.

Abstract. Aldosterone secretion rate (ASR) and plasma renin activity (PRA) on normal sodium and potassium intakes have been measured simultaneously in 14 normal subjects, 14 non‐malignant essential hypertensive patients, three malignant essential hypertensive patients, eight renovascular hypertensive patients, two parenchymatous renal hypertensive patients and five patients with primary hyperaldosteronism. The effect of salt loading was investigated in the two latter groups. In all groups of hypertensive patients the frequency of increased ASR was high. Fifity per cent of essential non‐malignant hypertensive patients had an ASR above normal range. There was no correlation between ASR and the grade of eyeground changes in essential hypertensive patients. Excluding patients with primary hyperaldosteronism a pronounced linear correlation between PRA and ASR was found. This indicated that the increased ASR in these groups of hypertensive patients is secondary to renin stimulation. Primary hyperaldosteronism was diagnosed by a PRA/ASR ratio differing significantly from the normal correlation. Failure of salt loading to depress ASR was not specific for primary hyperaldosteronism. In only two of five patients with abnormal PRA/ASR ratio was a solitary adenoma found. Removal of the tumour cured one of them. In the other three patients the adrenals showed adenomatous hyperplasia, and unilateral adrenalectomy had no effect. It is concluded that the best criterion for primary hyperaldosteronism at present is a deviation of the PRA/ASR ratio from the normal correlation, but differentiation between classical aldosteronoma and adenomatous hyperplasia of the adrenal gland is not as yet possible.

Measurement of the normal and hypertensive heart and great vessels based on cardiosynchronous angiocardiography

The development of angiocardiography is remarkable and it has become to be extensively applied to clinical diagnosis, but criteria of measurement in the angiocardiogram of normal adults, which are available for routine clinical diagnosis, have not been established yet. This paper aims to set up the criteria of the average values of measurements of normal hearts and the great vessels at the period of the end-diastolic and the systoic phase, by means of cardio-synchronous angiocardiography. As to the average value of measurements and contractility of normal hearts, not only the physiological changes were clarified by analizing the relations among age, sex and blood pressure, but also the vital function of normal hearts could be studied by thorough investigation of the correlation among all the measurements and the interrelation of measurements. Moreover, the difference between normal hearts and hypertensive ones was investigated statistically. Methods and Materials As normal subjects, one hundred and sixteen male and female adults ranged in age from 16 to 66 years (27.1 years on the average) were selected, whose blood pressures were lower than 149 mmHg at the systolic and 89 mmHg at the diastolic. As the hypertensive subjects, fifty-two male and female adults ranged in age from 18 to 65 years (45.6 years on the average) were selected, whose blood pressures were higher than 150 mmHg at the systolic and 90mmHg at the diastolic. And they were limited to those who were renal or essential hypertensive patients. The angiocardiograms were taken in the left anterior 70-degree oblique projection at the end-diastolic and the systolic phase. As for contrast mediurn, 80 per cent Angioconray or 75 per cent Urokolin M was injected intravenously, 1ml. per 1kg of the body weight. The parts to be measured were as follows :

The metabolism of angiotension II.

1. I 131 -labeled angiotensin II has been employed to study the metabolism of this polypeptide. 2. Following the intravenous administration of angiotensin II-I 131 to normotensive and untreated primary benign hypertensive subjects, a slower angiotensin II degradation rate and a larger final volume of distribution of angiotensin II-I 131 was found in the hypertensive than in the normotensive patients. The slow rate of degradation of angiotensin II may be responsible for the increased quantity and concentration of this polypeptide in the body fluids. 3. Greater quantities of angiotensin II-I 131 are degraded in vitro by sera from untreated primary benign hypertensive patients than from normotensive or secondary renal hypertensive patients. There is evidence for the presence of a serum factor or factors enhancing angiotensin II-I 131 degradation and for the presence of a heat labile inhibitor.

In vitro degradation of I-131 labeled angiotensin II by normotensive and hypertensive human serum.

SummaryRefrigeration of angiotensin II-I131in vitro with human sera from normotensive, untreated primary benign hypertensive and secondary renal hypertensive subjects demonstrated that greater quantities of angiotensin II-I131 were degraded by the untreated primary benign hypertensive patients than by the normotensive or secondary renal hypertensive patients. Evidence for presence of a serum factor (or factors) enhancing angiotensin II-I131 degradation and for a heat labile inhibitor has been advanced. The greater in vitro degradation of angiotensin II-I131 by untreated primary benign hypertensive patients than by normotensive subjects contrasts with the in vivo turnover rates.

CEREBRAL CIRCULATION AND METABOLISM IN HYPERTENSION

Measurements of cerebral hemodynamics and cerebral oxygen consumption (CMRO2) were made by the nitrous oxide method in 60 patients with essential hypertension.The mean values for cerebral blood flow (CBF) and CMRO2 were significantly lower (P<0.05) than normal values noted for healthy young men. The mean cerebral vascular resistance (CVR) was significantly higher than normal value (P<0.01). In these hypertensive patients the influence of aging on cerebral hemodynamics was studied, and statistically significant correlations was calculated between age and such values as CBF CVR and CMRO2. These findings revealed a decreasing CBF and CMRO2 and an increasing CVR accompanied with advancing age.Comparing these values in hypertensive patients with those in normotensive subjects of the same age, the statistically significant difference was only the significantly increased CVR (P<0.01). The effects of aging on the cerebral hemodynamics in the hypertensive group were more remarkable than that in the normotensive group. These facts were atributed to the more progressive increase of cerebral arteriosclerosis with advancing age in hypertension. The cerebral hemodynamic changes in seven renal hypertensive patients and one patient with coarctation of the aorta were the same with that of essential hypertensive prtients. In five hypertensive arteriosclerotic patients with psychosis CBF and CMRO2 were significantly decreased.There was no relationship between mean arterial blood pressure and CBF and the former and CMRO2. The relation between cerebral hemodynamics and the Keith-Wagener's grade were significant. The proportional increasing cerebral vascular resistance was observed accompanying with advancing in the grade.The cerebral vascular reactivity due to the inhalation of 5 per cent carbon dioxide in essential hypertensive patients was significant.These findings demonstrated that the CVR in hypertension was increased, mostly due to increased cerebral arteriolar tone, but partly due to arteriosclerosis.Finally, clinical implications of these studies were briefly discussed.