High plasma aldosterone and low renin predict blood pressure increase and hypertension in middle-aged Caucasian populations.

Plasma aldosterone and renin levels have been associated with blood pressure increase and 3-4 year incidence of hypertension in a middle-aged North American community in Framingham. To confirm these findings in a different population, a nested case-control study was performed in a national sample of 1984 French non-hypertensive volunteers aged 45-64 year and followed for 5 years. Cases and controls (individuals becoming hypertensive or remaining non-hypertensive on follow-up) were individually matched on sex, diastolic and systolic pressures at baseline. Multivariable regression models show that plasma aldosterone and renin are respectively positively and negatively associated with the increase in systolic pressure (P=0.01 and 0.001) and the risk of hypertension (22% increase and 16% decrease per s.d. increment in the log, P=0.04 and 0.07). These associations are mostly observed in the lowest tertiles of dietary sodium and potassium intakes where plasma aldosterone is positively associated with the increase in systolic pressure (P=0.01 and 0.08) and the risk of hypertension (59 and 69% increase per s.d. increment in the log, P=0.02 and 0.01), whereas plasma renin is negatively associated with the increase in systolic pressure (P=0.0004 and 0.004) and the risk of hypertension (31 and 28% decrease per s.d. increment in the log, P=0.03 and 0.05). These results reinforce the hypothesis that high plasma aldosterone and low plasma renin levels precede blood pressure increase and the occurrence of hypertension in middle-aged Caucasian populations.

Cardioprotection and kallikrein-kinin system in acute myocardial ischaemia in mice.

1. Acute myocardial ischaemia and reperfusion trigger cardioprotective mechanisms that tend to limit myocardial injury. These cardioprotective mechanisms remain for a large part unknown, but can be potentiated by performing ischaemic preconditioning or by administering drugs such as angiotensin-I-converting enzyme (kininase II) inhibitors (ACEI). 2. This brief review summarizes the findings concerning the role of tissue kallikrein (TK), a major kinin-forming enzyme, kinins and kinin receptors in the cardioprotection afforded by ischaemic preconditioning (IPC) or by pharmacological postconditioning by drugs originally targeted at the renin-angiotensin system, ACEI and type 1 angiotensin-II receptor blockers (ARB) in acute myocardial ischaemia. Myocardial ischaemia was induced by left coronary occlusion and was followed after 30 min by a 3 h reperfusion period (IR), performed in vivo in mice. The role of the kallikrein-kinin system (KKS) was studied by using genetically engineered mice deficient in TK gene and their wild-type littermates, or by blocking B1 or B2 bradykinin receptors in wild-type mice using selective pharmacological antagonists. 3. Ischaemic preconditioning (three cycles: 3 min occlusion/5 min reperfusion) enhances the ability of the heart of wild-type mice to tolerate IR. Tissue kallikrein plays a major role in the cardioprotective effect afforded by IPC, which is largely reduced in TK-deficient mice. The B2 receptor is the main kinin receptor involved in the cardioprotective effect of IPC. 4. Tissue kallikrein is also required for the cardioprotective effects of pharmacological postconditioning with ACEI (ramiprilat) or ARB (losartan), which are abolished for both classes of drugs in TK-deficient mice. The B2 receptor mediates the cardioprotective effects of these drugs. Activation of angiotensin-II type 2 (AT2) receptor is involved in the cardioprotective effects of losartan, suggesting a functional coupling between AT2 receptor and TK during angiotensin-II type 1 (AT1) receptor blockade. 5. The demonstration of a cardioprotective effect of the KKS in acute myocardial ischaemia involving TK and the B2 receptor and playing a major role in IPC or pharmacological postconditioning by ACEI or ARB, suggests a potential therapeutic approach based on pharmacological activation of the B2 receptor.

Morphometric evidence for impairment of renal autoregulation in advanced essential hypertension.

A morphometric study was performed on 22 renal biopsies from hypertensive patients with proteinuria and/or azotemia, with no evidence of other renal disease. These results were compared with our earlier study of normotensive aging kidneys. Afferent arterioles in hypertensive kidneys showed a significant increase in lumen diameter (15.7+/-4.9 vs 13.4+/-4.7 microm, P=0.0007) and wall area (1234+/-769 vs 998+/-445 microm(2), P=0.037), due primarily to shift in the distribution of arteriolar types, from predominantly normal toward predominantly hyaline arterioles in hypertension. Glomeruli were divided into four basic types: normal, hypertrophic, focal segmental glomerulosclerosis (FSGS) type, and sclerosing. Overall, glomeruli in hypertensive kidneys were much larger than in normotensive aging kidneys, for example, total capillary area (16 247+/-10 681 vs 11 624+/-5702 microm(2), P<0.00001). This increase was due primarily to an increase in size of each type, for example, for hypertrophic glomeruli: total capillary area (22 205+/-10 426 vs 15 349+/-4577 microm(2), P=0.0038). There was an excellent correlation between arteriolar lumen diameter and mean glomerular capillary area for hypertrophic/FSGS-type glomeruli (r=0.4778, P=0.0013), such that as arteriolar diameter increases the mean glomerular capillary area increases, consistent with loss of autoregulation. The morphologic correlates of loss of autoregulation, with afferent arteriolar dilatation and increase in glomerular capillary size, glomerular hypertrophy, and subsequent FSGS, are present on a focal basis in aging kidneys and, much more extensively, although still focally, in hypertensive kidneys.

Role of tissue kallikrein in the cardioprotective effects of ischemic and pharmacological preconditioning in myocardial ischemia.

Tissue kallikrein (TK), a major kinin-forming enzyme, is synthesized in the heart and arteries. We tested the hypothesis that TK plays a protective role in myocardial ischemia by performing ischemia-reperfusion (IR) injury, with and without ischemic preconditioning (IPC) or ACE inhibitor (ramiprilat) pretreatment, in vivo in littermate wild-type (WT) or TK-deficient (TK-/-) mice. IR induced similar infarcts in WT and TK-/-. IPC reduced infarct size by 65% in WT, and by 40% in TK-/- (P<0.05, TK-/- vs WT). Ramiprilat also reduced infarct size by 29% in WT, but in TK-/- its effect was completely suppressed. Pretreatment of WT with a B2, but not a B1, kinin receptor antagonist reproduced the effects of TK deficiency. However, B2 receptor-deficient mice (B2-/-) unexpectedly responded to IPC or ramiprilat like WT mice. But pretreatment of the B2-/- mice with a B1 antagonist suppressed the cardioprotective effects of IPC and ramiprilat. In B2-/-, B1 receptor gene expression was constitutively high. In WT and TK-/- mice, both B2 and B1 mRNA levels increased several fold during IR, and even more during IPC+IR. Thus TK and the B2 receptor play a critical role in the cardioprotection afforded by two experimental maneuvers of potential clinical relevance, IPC and ACE inhibition, during ischemia.

Survival, haemodynamics and cardiac remodelling follow up in mice after myocardial infarction.

1. In the present study, the time-course, over a 1 year period, of postischaemic dilated cardiomyopathy and/or development of congestive heart failure was investigated in mice in terms of survival and cardiac functional and structural characteristics. 2. C57BL/6 mice with myocardial infarction (MI mice; coronary ligation n = 78) or sham-operated animals (n = 45) were used and echocardiographic, haemodynamic and histomorphometric parameters were assessed at 3, 6 and 12 months post-MI. 3. At 12 months, the survival rate was 70% in MI mice. Left ventricular dysfunction was evidenced by a strong decrease in ejection fraction (EF; -48 and -53% at 6 and 12 months, respectively; both P < 0.05) and an increase in left ventricular end-diastolic pressure (+100% at both 6 and 12 months; both P < 0.05). There was no major worsening in cardiac function between 6 and 12 months, suggesting strong compensatory mechanisms. Cardiac remodelling was observed, characterized by strong left ventricular hypertrophy (+38 and +62% at 6 and 12 months, respectively; both P < 0.05) and dilatation (+53% at 6 months; P < 0.05), but collagen was not significantly increased. Significant correlations were found between EF (echocardiography) and dP/dtmax, between end-diastolic volume (echocardiography) and left ventricular internal perimeter (histomorphometry) and between left ventricular mass (echocardiography) and weight. 4. In conclusion, despite a high survival rate, the MI mouse model displays most of the hallmarks of postischaemic dilated cardiomyopathy and/or congestive heart failure, thus affording the necessary background for the subsequent evaluation of gene manipulation and/or drug effects. In addition, two-dimensional echocardiography appears to be a suitable tool for the long-term follow up of cardiac function and remodelling in this model.

Age-related changes in urethrovesical coordination in male rats: relationship with bladder instability?

The micturition profile in conscious animals and the urethrovesical coordination in anesthetized conditions were investigated in 6- and 24-mo-old male Sprague-Dawley rats. The in vitro pharmacological responses to KCl, electrical field stimulation (EFS), carbachol, phenylephrine, and isoprenaline were determined in the isolated bladder body, the bladder neck, and urethra. A morphometric and immunohistological study has been included. During conscious cystomanometry, 63% of the aging rats but only 25% of the adult rats showed spontaneous contractions during the bladder-filling phase. In conscious aging rats, basal pressure, threshold pressure, and micturition pressure were also significantly increased. In anesthetized aging rats, a decrease in resting urethral pressure at micturition threshold and the occurrence of a significant delay in urethral relaxation during micturition were associated with an increased residual volume. In all isolated tissues, contractile response to KCl was not modified with aging, whereas age-related decreases in maximal responses to carbachol in the bladder body and to phenylephrine and carbachol in the urethra were observed. In the bladder neck only, we found a significant decrease in the amplitude of neurogenic contractions associated with fibrosis but without decrease in nerve density. These experiments show significant modifications in the voiding pattern of aging rats associated with urethral dysfunction and with regionally specific pharmacological and structural changes of the urinary tract. We propose that aging in rats is characterized by an impairment of the urethrovesical coordination, leading to bladder dysfunctions similar to those induced by bladder outlet obstruction.

Genetically increased angiotensin I-converting enzyme level and renal complications in the diabetic mouse.

Diabetic nephropathy is a major risk factor for end-stage renal disease and cardiovascular diseases and has a marked genetic component. A common variant (D allele) of the angiotensin I-converting enzyme (ACE) gene, determining higher enzyme levels, has been associated with diabetic nephropathy. To address causality underlying this association, we induced diabetes in mice having one, two, or three copies of the gene, normal blood pressure, and an enzyme level range (65-162% of wild type) comparable to that seen in humans. Twelve weeks later, the three-copy diabetic mice had increased blood pressures and overt proteinuria. Proteinuria was correlated to plasma ACE level in the three-copy diabetic mice. Thus, a modest genetic increase in ACE levels is sufficient to cause nephropathy in diabetic mice.

Inflammation is probably not a prerequisite for renal interstitial fibrosis in normoglycemic obese rats.

We examined the role of inflammation in the development of renal interstitial fibrosis in Zucker obese rats, which rapidly present kidney lesions in the absence of hypertension and hyperglycemia. Type I and III collagens were quantified using a polarized light and computer-assisted image analyzer. The expression of mRNA encoding matrix components, adhesion molecules, chemokines, and growth factors was followed by RT-PCR. The presence of synthesized proteins as well as lymphocytes and macrophages was determined by immunohistochemistry. Interstitial fibrosis developed in two phases. The first phase occurred as early as 3 mo and resulted from a neosynthesis of type III collagen and fibronectin and a reduction of extracellular matrix catabolism, in parallel with an overexpression of transforming growth factor-beta(1) and in the absence of any lymphocyte or macrophage infiltration. After 6 mo, interstitial fibrosis worsened with a large accumulation of type I collagen, concomitantly with a large macrophage infiltration. Thus inflammation cannot explain the onset of interstitial fibrosis that developed in young, insulinoresistant, normoglycemic, obese Zucker rats but aggravated this process afterward.

Cardiovascular abnormalities with normal blood pressure in tissue kallikrein-deficient mice.

Tissue kallikrein is a serine protease thought to be involved in the generation of bioactive peptide kinins in many organs like the kidneys, colon, salivary glands, pancreas, and blood vessels. Low renal synthesis and urinary excretion of tissue kallikrein have been repeatedly linked to hypertension in animals and humans, but the exact role of the protease in cardiovascular function has not been established largely because of the lack of specific inhibitors. This study demonstrates that mice lacking tissue kallikrein are unable to generate significant levels of kinins in most tissues and develop cardiovascular abnormalities early in adulthood despite normal blood pressure. The heart exhibits septum and posterior wall thinning and a tendency to dilatation resulting in reduced left ventricular mass. Cardiac function estimated in vivo and in vitro is decreased both under basal conditions and in response to beta-adrenergic stimulation. Furthermore, flow-induced vasodilatation is impaired in isolated perfused carotid arteries, which express, like the heart, low levels of the protease. These data show that tissue kallikrein is the main kinin-generating enzyme in vivo and that a functional kallikrein-kinin system is necessary for normal cardiac and arterial function in the mouse. They suggest that the kallikrein-kinin system could be involved in the development or progression of cardiovascular diseases.

Towards content-based image retrieval in a HIS-integrated PACS.

Development of a Picture Archiving and Communications System (PACS) with a large and diverse set of medical images will lead to large digital libraries that can be accessed to provide improved support for patient care, research and education. New representational and retrieval models for clinical images are required to address these issues. The PACS at the Georges Pompidou Hospital (GPH) is integrated in the hospital information system (HIS), and several modalities from medical imaging departments have been attached to it. The two main axes of the GPH PACS project were 1) HIS-integration to allow hospital-wide access to the images based on demographic and procedure-type information and 2) the development of content-based image retrieval to enhance the medical impact of image retrieval in daily practice.

Early glomerular macrophage recruitment in streptozotocin-induced diabetic rats.

Diabetic glomerulosclerosis is defined by increased glomerular extracellular matrix (ECM) that is mainly synthesized by mesangial cells that underwent an activation mediated by cytokines and growth factors from various cellular origins. In this study, we tested whether macrophages could infiltrate the glomeruli and influence ECM synthesis in experimental diabetes. To test our hypothesis, we initially studied the dynamics of glomerular macrophage recruitment in streptozotocin-induced diabetic rats at days 1, 2, 4, 8, 15, and 30 by using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) on isolated glomeruli and immunohistochemistry and morphometry. We then assessed the role of macrophages on the basis of the pharmacological modulation of their recruitment by insulin or ACE inhibitor treatments and by X-irradiation-induced macrophage depletion at days 8 and 30. Macrophages were recruited within the glomeruli at the very early phase of hyperglycemia by using RT-PCR CD14 detection from day 2 and by using ED1 immunohistochemistry from day 8. This glomerular macrophage infiltration was associated with an increase in alpha1-chain type IV collagen mRNA. In parallel, the diabetic glomeruli became hypertrophic with an increase in the mesangial area. Macrophage recruitment was preceded by or associated with an increased glomerular expression of vascular cell adhesion molecule 1, intracellular adhesion molecule 1, and monocyte chemoattractant protein 1, which contributes to monocyte diapedesis. Glomerular interleukin-1beta mRNA synthesis was also enhanced as early as day 1 and could be involved in the increase in ECM and adhesion molecule gene expressions. Insulin treatment and irradiation-induced macrophage depletion completely prevented the glomerular macrophage recruitment and decreased alpha1-chain type IV collagen mRNA and mesangial area in diabetic rats, whereas ACE inhibitor treatment had an incomplete effect. It can be concluded that in the streptozotocin model, hyperglycemia is followed by an early macrophage recruitment that contributes to the molecular and structural events that could lead to glomerulosclerosis. Therefore, besides direct stimulation of mesangial cells by hyperglycemia, macrophages recruited in the glomeruli during the early phase of hyperglycemia could secondarily act on mesangial cells.

Functional and morphological modifications of the urinary bladder in aging female rats.

In female Wistar/Rij rats, 10 and 30 mo old, the micturition profiles in conscious animals, the contractile responses of the isolated urinary bladder, and the histology of the vesical tissue have been investigated. During cystomanometry, 60% of conscious senescent rats, but only 25% of young adult rats, showed spontaneous contractions during the bladder-filling phase. In aging rats, micturition pressure and duration of micturition were significantly higher by approximately 40-50%. In contrast, bladder capacity, bladder compliance, micturition volume, and residual volume were not modified with age. In vitro, the contractile responses of the bladder body to KCl, carbachol, arecoline, and alpha,beta-MeATP were similar in tissues from young adult and senescent rats. In contrast, maximum responses to noradrenaline, but not phenylephrine, were two times greater in the older rats. Isoprenaline exhibited the same potency in relaxing KCl-precontracted bladder body of 10- and 30-mo-old animals. Morphometric analysis showed a significant increase in the mean thickness of the muscularis layer with age, whereas the collagen density significantly decreased in the muscularis and in the lamina propria layers. The fact that the majority of senescent rats displayed bladder instability and increased response to alpha-adrenergic agonists suggests that this strain of rat seems a good model for the aged human. However, other characteristics of the aging human urinary tract (urinary frequency, decreased cystometric capacity, and decreased detrusor contractility associated with fibrosis) are not present.

Altered control of self-reactive IgG by autologous IgM in patients with warm autoimmune hemolytic anemia.

Warm autoimmune hemolytic anemia (WAIHA) is characterized by an accelerated clearance of red blood cells (RBCs) associated with the presence of anti-RBC immunoglobulin (Ig)G autoantibodies. In the present study, we analyzed the self-reactive IgG and IgM antibody repertoires of patients with WAIHA using a technique of quantitative immunoblotting on a panel of whole tissue extracts as sources of self-antigens. Data were compared by means of multiparametric statistical analysis. We demonstrate that self-reactive antibody repertoires of IgG purified from plasma and of IgG purified from RBC eluates do not differ between healthy donors and patients with WAIHA, whereas autoreactive repertoires of IgM from patients exhibit broadly altered patterns of reactivity as compared with those of healthy controls. We further demonstrate that IgG purified from eluates of RBCs of healthy donors induces agglutination of RBCs in an indirect Coombs assay to a similar extent as IgG purified from eluates of RBCs of patients with WAIHA. The capability of IgG to induce agglutination of RBCs is suppressed in unfractionated eluates of healthy donors' cells, whereas it is readily found in unfractionated eluates of patients' RBCs. IgM is an essential factor in controlling the ability of IgG in unfractionated RBC eluates to induce agglutination of RBCs. These observations indicate that anti-RBC IgG autoantibodies of patients with WAIHA share extensive similarity with natural antiRBC autoantibodies of healthy donors and suggest that defective control of IgG autoreactivity by autologous IgM is an underlying mechanism for autoimmune hemolysis in WAIHA. (Blood. 2000;95:328-335)

A visual coding system in histopathology and its consensual acquisition.

Divergent descriptions of histopathologic images induce inter- and intra-observer variability in diagnosis. Even though a controlled terminology exists to describe medical imaging, pathologists do not always agree on the visual representation of the descriptive terms. The main purpose of our work is to define a methodology to build a standardized visual coding system unambiguously characterizing the terms of a microglossary. The methodology follows two steps: 1) the acquisition of experts' descriptions of images using the microglossary and 2) a consensus derivation. The procedure was applied on a set of 85 histopathological images of breast tumors described by two experts. Among the 339 objects selected in images, 176 were detected by both experts, 77% localized at the same place and 25% also identically labeled. The microglossary was enriched and illustrated via the resulting consensual descriptions. The contribution of this work supports relevant indexing of biomedical images and image-related information.

Mibefradil prevents L-NAME-exacerbated nephrosclerosis in spontaneously hypertensive rats.

OBJECTIVE: To determine the potential renal protective effects of a novel calcium channel blocker mibefradil in chronic renal failure. METHOD: We compared the long-term effects of mibefradil with an angiotensin-converting enzyme inhibitor cilazapril on blood pressure, proteinuria, renal function and histological alterations in N-nitro-L-arginine methylester (L-NAME)-treated spontaneously hypertensive rats (SHR). Three groups of SHR were studied for 45 days: group 1 (n = 14), treated with L-NAME only (50 mg/l in the drinking water); group 2 (n = 15) L-NAME plus co-treatment with mibefradil (30 mg/kg per day); group 3 (n = 15), L-NAME plus co-treatment with cilazapril (10 mg/kg per day). RESULTS: Both mibefradil and cilazapril attenuated the increased systolic blood pressure, and prevented the development of proteinuria and the decreased creatinine clearance (Ccr) seen at day 42 in the group treated with L-NAME alone. Notably, mibefradil had similar effects to cilazapril on proteinuria and Ccr, despite a reduced antihypertensive effect All animals receiving mibefradil co-treatment remained alive throughout the experiment, whereas the mortality rate was 43% in SHR treated with L-NAME alone. Both mibefradil and cilazapril completely prevented renal structural damage as assessed by scoring glomerular, tubulo-interstitial and vascular lesions. CONCLUSIONS: Our data show that mibefradil prevented the development of hypertension and proteinuria, renal functional impairment and nephrosclerosis, and also improved animal survival. The renal protective effects of mibefradil were at least equivalent to those of an ACE inhibitor in this animal model of chronic renal failure.

Effects of nonpeptide endothelin receptor antagonists in rats with reduced renal mass.

This study was set up to evaluate the long-term effects of nonpeptide endothelin (ET) antagonists in rats with renal mass reduction (RMR). In the first series of experiments, rats were administered bosentan (100 mg/kg/day) or the angiotensin-converting enzyme inhibitor cilazapril (10 mg/kg/day) for 14 weeks beginning 24 h after RMR. As expected, cilazapril completely prevented the development of hypertension, proteinuria, and renal structural damage. In contrast, bosentan had no influence on the development of proteinuria and renal structural damage, although it had a moderate antihypertensive effect and improved creatinine clearance. A second set of experiments was performed to assess whether Ro 48-5695, a very potent ET antagonist optimized from bosentan, could prevent the development of renal damage and reverse established renal damage. Rats received Ro 48-5695 (30 mg/kg/day) beginning either 24 h (prevention) before for 8 weeks, or 4 weeks (reversal) after RMR. Ro 48-5695 attenuated the hypertension and the decline of creatinine clearance when treatment was started at 24 h, but not when started at 4 weeks. Ro 48-5695 had no effect on proteinuria. These observations suggest that ET-receptor activation does not play a major role in the progression of glomerular sclerosis in this model of chronic renal failure.

Expert consultation for cervical carcinoma smears. Reliability of selected-field videomicroscopy.

OBJECTIVE: To evaluate the diagnostic accuracy of videomicroscopy image selection for expert consultation in cervical cytology. STUDY DESIGN: One hundred diagnostically difficult cervical cytologic smears were selected and rescreened by a general pathologist who chose, from each slide, four or five fields featuring abnormal cells. Video images were digitized and stored on a 512 x 512-pixel matrix using an image acquisition and transmission system. Five experts each reviewed 20 of the 100 cases, and a sixth reviewed all 100 cases. Diagnoses based on selected digitized images were compared to those based on conventional examination of whole slides. RESULTS: Intraobserver agreement was fair to excellent for all six experts (kappa value: 0.47-0.81); it was complete or acceptable in 68.4-85% of cases. Compared to the reference diagnosis, interobserver agreement was not significantly different whether cases were examined by screening the entire slide or by videomicroscopy of selected fields. The marked discordance in four cases concerned very small cells the significance of which was misinterpreted on videomicroscopy because of poor image quality due to lack of focus setting. CONCLUSION: This exploratory study showed that selection of videomicroscopy images seems as reliable as conventional examination of slides for expert consultation on diagnostically difficult cervical cytologic smear cases.