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.

GHEP-ISFG collaborative exercise on mixture profiles (GHEP-MIX06). Reporting conclusions: Results and evaluation.

One of the main goals of the Spanish and Portuguese-Speaking Group of the International Society for Forensic Genetics (GHEP-ISFG) is to promote and contribute to the development and dissemination of scientific knowledge in the field of forensic genetics. Due to this fact, GHEP-ISFG holds different working commissions that are set up to develop activities in scientific aspects of general interest. One of them, the Mixture Commission of GHEP-ISFG, has organized annually, since 2009, a collaborative exercise on analysis and interpretation of autosomal short tandem repeat (STR) mixture profiles. Until now, six exercises have been organized. At the present edition (GHEP-MIX06), with 25 participant laboratories, the exercise main aim was to assess mixture profiles results by issuing a report, from the proposal of a complex mock case. One of the conclusions obtained from this exercise is the increasing tendency of participating laboratories to validate DNA mixture profiles analysis following international recommendations. However, the results have shown some differences among them regarding the edition and also the interpretation of mixture profiles. Besides, although the last revision of ISO/IEC 17025:2017 gives indications of how results should be reported, not all laboratories strictly follow their recommendations. Regarding the statistical aspect, all those laboratories that have performed statistical evaluation of the data have employed the likelihood ratio (LR) as a parameter to evaluate the statistical compatibility. However, LR values obtained show a wide range of variation. This fact could not be attributed to the software employed, since the vast majority of laboratories that performed LR calculation employed the same software (LRmixStudio). Thus, the final allelic composition of the edited mixture profile and the parameters employed in the software could explain this data dispersion. This highlights the need, for each laboratory, to define through internal validations its criteria for editing and interpreting mixtures, and to continuous train in software handling.

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.

Murine models of myocardial and limb ischemia: diagnostic end-points and relevance to clinical problems.

Ischemic disease represents the new epidemic worldwide. Animal models of ischemic disease are useful because they can help us to understand the underlying pathogenetic mechanisms and develop new therapies. The present review article summarizes the results of a consensus conference on the status and future development of experimentation in the field of cardiovascular medicine using murine models of peripheral and myocardial ischemia. The starting point was to recognize the limits of the approach, which mainly derive from species- and disease-related differences in cardiovascular physiology. For instance, the mouse heart beats at a rate 10 times faster than the human heart. Furthermore, healing processes are more rapid in animals, as they rely on mechanisms that may have lost relevance in man. The main objective of the authors was to propose general guidelines, diagnostic end points and relevance to clinical problems.

Detection of a mutator phenotype in cancer cells by inter-Alu polymerase chain reaction.

A mutator phenotype due to a DNA mismatch repair deficiency is usually detected by typing a number of microsatellite markets. Here, eight hereditary nonpolyposis colon cancer patients with microsatellite instability were investigated by inter-Alu PCR, known to amplify DNA segments that may represent preferential targets of replication errors. Among 40-60 bands revealed in a single PCR experiment, more than 20% were found altered in tumoral DNA samples compared to matched normal samples from the same patient. Shifts and changes in signal intensity accounted for most of the alterations, whereas gains or losses of bands were rare. Certain bands were affected only in a single patient, whereas the instabilities in others were common. These results suggest that some genomic regions are more susceptible than others to the expression of a mutator phenotype. Four such bands altered in at least five patients were characterized further and shown to be unstable because of contractions of the Alu poly(A) tails. Interestingly, none of the bands representing loci shown previously to be polymorphic in the population displayed instability in the tumoral samples. Inter-Alu PCR appears to be a robust, cost-effective, and sensitive technique for revealing the mutator phenotype in cancer cells.

Alu RNA transcripts in human embryonal carcinoma cells. Model of post-transcriptional selection of master sequences.

Alu master sequences colonized the human genome using RNA as amplification intermediate. To understand this phenomenon better we isolated and analyzed Alu RNA from NTera2D1 pluripotential cells. Northern hybridization, primer extension, cDNA cloning and sequencing data are congruent and demonstrate a low level of Alu specific transcription. These bona fide RNA Polymerase III Alu transcripts, although enriched in the cytoplasm, are not dominated by a single master species but rather originate from a variety of loci. However, when compared with the genomic average, or to repeats from RNA Polymerase II co-transcripts, they belong to the youngest group of Alu subfamilies (p less than 0.001) and have a higher content of intact CpG-dinucleotides. This suggests that Alu transcription is influenced both by mutations and the genomic context, and points to a possible role of DNA methylation in silencing the bulk of genomic repeats. Because of the heterogeneity of Alu transcripts a post-transcriptional selection mechanism recruiting Alu master sequences for retroposition is required. We propose that Alu RNA masters could have evolved as selfish satellites to a more complex retroposition system equipped with a reverse transcriptase activity and that their structure was conserved through "phenotypic" selection of the RNA level.

Effects of long-term angiotensin II AT1 receptor blockade on survival, hemodynamics and cardiac remodeling in chronic heart failure in rats.

OBJECTIVE: The beneficial effect of chronic angiotensin I converting enzyme (ACE) inhibition on survival has for long been established in the rat post-infarction model of chronic heart failure (CHF) and has subsequently been confirmed in humans. This study investigates in rats whether chronic angiotensin II AT1 receptor blockade shares with ACE inhibition the same beneficial effect. METHODS: Rats we subjected to coronary artery ligation and, from 7 days later, orally treated for 7.5 months with placebo or irbesartan (5 or 50 mg/kg/day). RESULTS: Irbesartan dose-dependently increased survival (placebo: 27%, low dose: 52%, high dose: 82%, sham-ligated: 100%; high dose vs placebo: P < 0.001 and vs low dose: P < 0.05; low dose vs placebo: P = 0.11). Irbesartan also dose-dependently decreased urinary cyclic GMP excretion throughout the study. At 7.5 months, it dose-dependently decreased left ventricular (LV) end diastolic pressure. normalized LV pressure maximal rate of rise (dP/dt) and cardiac index values and improved LV and right ventricular regional blood flows (radioactive microspheres) and resistances. At 7.5 months, irbesartan markedly decreased myocardial hypertrophy but had almost no effect on LV dilatation and subendocardial fibrosis. CONCLUSIONS: Long-term angiotensin II AT1 receptor blockade with irbesartan strongly and dose-dependently increases survival in the rat model of coronary ligation-induced CHF. This effect is due to the combination of the beneficial effects that the drug exerts on systemic and coronary hemodynamics, on cardiac pump function and vs cardiac hypertrophy development. Long-term AT1 receptor blockade might thus prove useful and prolong survival in human CHF.

Decreased type VI adenylyl cyclase mRNA concentration and Mg(2+)-dependent adenylyl cyclase activities and unchanged type V adenylyl cyclase mRNA concentration and Mn(2+)-dependent adenylyl cyclase activities in the left ventricle of rats with myocardial infarction and longstanding heart failure.

OBJECTIVE: To address the effect of longstanding left ventricular (LV) hypertrophy and failure on LV adenylyl cyclase (AC) gene expression, mRNA concentrations of the main cardiac AC isoforms were measured in the non-infarcted area of LV from rats with myocardial infarction (MI), without (H) or with (F) LV failure, and in control (C) rats. Basal, GTP- and forskolin-stimulated Mg(2+)- and Mn(2+)-dependent AC activities were also measured in F and C rats. METHODS: Two- and six months after MI, steady-state AC mRNA concentrations were assessed by Northern blot analysis and RNase protection assay with isoform-specific cDNA and cRNA probes, respectively. AC activities were assessed on LV microsomal fractions using standard procedures. RESULTS: Types V and VI, and types IV and VII were the major and minor AC mRNA isoforms in both the LVs of F and C rats. Two months after MI, no difference in LV type V or VI mRNA to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA ratios was observed in rats with H or F compared to C. Six months after MI, no difference in LV type V mRNA concentration was observed between the three rat groups, whether this level was normalized to GAPDH, poly-(A+) or 18S RNAs. In contrast, a 35% decrease in the type VI mRNA to poly-(A+) RNA ratio and a 29% decrease in the type VI mRNA to 18S RNA ratio was observed only in rats with F compared to C (p < 0.05 vs. C for the two comparisons). Two- and six months after MI, basal and forskolin-stimulated Mg(2+)-dependent AC activities were decreased by 30-35% in F rats compared to C (p < 0.05), whereas Mn(2+)-dependent activities were unchanged. CONCLUSION: Longstanding LV hypertrophy and failure resulting from MI in rats is not associated with altered expression of the most abundant, type V, AC mRNA isoform, whereas that of type VI is decreased. The lack of change in Mn(2+)-dependent AC activities in the LV of F rats suggests that this decrease has no functional consequence on overall AC activity and that decreased Mg(2+)-dependent activities are related to alterations occurring upstream.

Tissue kallikrein is required for the cardioprotective effect of cyclosporin A in myocardial ischemia in the mouse.

Clinical and experimental studies suggest that pharmacological postconditioning with Cyclosporin A (CsA) reduces infarct size in cardiac ischemia and reperfusion. CsA interacts with Cyclophilin D (CypD) preventing opening of the mitochondrial permeability transition pore (mPTP). Tissue kallikrein (TK) and its products kinins are involved in cardioprotection in ischemia. CypD knockout mice are resistant to the cardioprotective effects of both CsA and kinins suggesting common mechanisms of action. Using TK gene knockout mice, we investigated whether the kallikrein-kinin system is involved in the cardioprotective effect of CsA. Homozygote and heterozygote TK deficient mice (TK(-/-), TK(+/-)) and wild type littermates (TK(+/+)) were subjected to cardiac ischemia-reperfusion with and without CsA postconditioning. CsA reduced infarct size in TK(+/+) mice but had no effect in TK(+/-) and TK(-/-) mice. Cardiac mitochondria isolated from TK(-/-) mice had indistinguishable basal oxidative phosphorylation and calcium retention capacity compared to TK(+/+) mice but were resistant to CsA inhibition of mPTP opening. TK activity was documented in mouse heart and rat cardiomyoblasts mitochondria. By proximity ligation assay TK was found in close proximity to the mitochondrial membrane proteins VDAC and Tom22, and CypD. Thus, partial or total deficiency in TK induces resistance to the infarct size reducing effect of CsA in cardiac ischemia in mice, suggesting that TK level is a critical factor for cardioprotection by CsA. TK is required for the mitochondrial action of CsA and may interact with CypD. Genetic variability in TK activity has been documented in man and may influence the cardioprotective effect of CsA.

Influence of captopril and enalapril on regional vascular alpha-adrenergic receptor reactivity in SHR.

The effects of short-term oral treatment with captopril and enalapril (two angiotensin-I-converting-enzyme inhibitors [ACEIs] that were administered in equipotent antihypertensive doses) on the systemic vasopressor response and on the renal, mesenteric, and hindlimb vascular responses to cirazoline and UK-14,304 (alpha 1- and alpha 2-adrenergic receptor-specific agonists, respectively) were investigated in adult pithed spontaneously hypertensive rats (SHR) of the Okamoto-Aoki strain. In the nonbinephrectomized animal, captopril and enalapril reduced to the same extent the systemic blood pressure and renal and hindlimb vascular resistances. They also decreased to the same extent systemic pressor and regional vasoconstrictor responses to cirazoline and UK-14,304, especially in the renal and mesenteric vascular beds. Simultaneously, the effects of angiotensin I and angiotensin II on the pressor response were abolished and almost not modified. In the binephrectomized animals, captopril and enalapril no longer reduced the systemic blood pressure and regional vascular resistances, but whereas the sympathoinhibitory effect of captopril vs the systemic pressor and regional vasoconstrictor responses to cirazoline and UK-14,304 persisted, those of enalapril disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of captopril and enalapril on regional vascular resistance and reactivity in spontaneously hypertensive rats.

The present study compares the effects of short-term treatments with captopril and enalapril, administered in equipotent antihypertensive doses, on the regional vascular resistances and on the regional vascular responsiveness to vasopressor agents of adult spontaneously hypertensive rats (SHRs). Three groups of animals were treated by gavage with captopril (100 mg/kg), enalapril (25 mg/kg), or distilled water for 8 days. Arterial blood pressure (BP), heart rate (HR), plasma renin concentration (PRC), and plasma converting-enzyme activity (CEA) were measured. Cardiac index (CI), total peripheral resistance (PR), and organ flow distribution were determined using microspheres. Renal and mesenteric vascular responsiveness to vasopressor agents was evaluated by continuous measurement of renal and mesenteric blood flows with miniaturized pulsed Doppler flow probes. Data showed that in the anesthetized SHR the two drugs induced similar reductions in BP, PR, and HR, without affecting CI. They simultaneously produced a strong converting-enzyme inhibition as evidenced by the suppression of angiotensin I effects accompanied by a potentiation of angiotensin II responses, a reduction in CEA, and an increase in PRC. Organ flows were similarly and homogeneously increased, especially in the kidneys, in both treated groups. Norepinephrine (NE) vasoconstrictor responses were abolished in the mesenteric vascular bed by both drugs, but in the renal, NE responses although completely abolished by captopril were only partially reduced by enalapril. It thus appears that diminished vascular responsiveness to NE, especially in the case of captopril, is probably involved along with converting-enzyme inhibition in the antihypertensive action of converting enzyme inhibitors (CEI), the mechanism of the difference between captopril and enalapril remaining still speculative.

Additive effects of enalapril and losartan in (mREN-2)27 transgenic rats.

Blockade of angiotensin II AT1 receptors combined with angiotensin I-converting enzyme inhibition might amplify the potency of the renin-angiotensin system blockade. We studied whether chronic and simultaneous administration of enalapril and losartan would result in additive or synergistic effects in the (mREN-2)27 transgenic rat (TGR), the investigated targets being blood pressure, cardiac hypertrophy, renin-angiotensin system blockade achieved, and plasma active renin concentration. In addition, the origin (renal or extrarenal, rat or mouse) of the induced renin release was determined. Adult TGRs were treated orally and daily for 5 to 7 weeks with 1 mg/kg (E1) or 3 mg/kg (E3) enalapril or 1 mg/kg (L1) or 3 mg/kg (L3) losartan, or their combinations (E1L1 and E3L3). At the end of the treatment period, enalapril and losartan exerted dose-dependent and, when combined, additive effects in terms of blood pressure fall and cardiac hypertrophy limitation, and synergistic effects in terms of plasma active renin stimulation and blockade of exogenous angiotensin I pressor effects, with E3L3>E3>L3, E1L1>E1> or =L1, and E1L1=E3>L3). This indicates that in the TGR, (1) the greater the renin-angiotensin system blockade achieved, the greater are the reduction in blood pressure, the limitation of cardiac hypertrophy, and the reactive rise in plasma renin concentration elicited, and (2) the enalapril-losartan combinations are more potent at achieving these goals than any of their constituents individually. In contrast, there was no interaction between the two drugs regarding aldosteronuria reduction. Measurement of plasma renin concentration and renal renin at pH 6.5 and 8.5, ie, the optimal pH values for rat and mouse renin activities, respectively, indicates that in TGRs the counterregulatory process for renin release elicited by enalapril, losartan, or their combination involves primarily rat renin of renal origin, a finding supported further by the observed increase in the rat renal renin hybridization index.

Theophylline kinetics and ventilatory flow in bronchial asthma and chronic airflow obstruction: influence of erythromycin.

The kinetics and the effects on the ventilatory function peak expiratory flow rate (PEFR) of a single 600-mg oral dose of theophylline were investigated in 46 adult patients with bronchial asthma (BA) and in 16 adult patients with chronic airflow obstruction (CAO). In the former, theophylline induced an early and potent bronchodilatation (60% rise in PEFR), the kinetics of which correlated with plasma concentration. Theophylline was also effective in patients with CAO, but the magnitude of its bronchodilator effect was less than in those with BA: this was despite plasma concentrations of much the same order. In adult patients with BA (but not with CAO) theophylline plasma levels and bioavailability are higher after simultaneous erythromycin dosing.

Genetic polymorphisms of N-acetyltransferases 1 and 2 and gene-gene interaction in the susceptibility to childhood acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. In utero and postnatal exposures to various carcinogens may play a role in the etiology of this disease. N-acetyltransferases, encoded by the NAT1 and NAT2 genes are involved in the biotransformation of aromatic amines present in tobacco smoke, environment, and diet. Their rapid and slow acetylation activity alleles have been shown to modify the risk to a variety of solid tumors in adults. To investigate the role of NAT1 and NAT2 variants as risk-modifying factors in leukemogenesis, we conducted a case-control study on 176 ALL patients and 306 healthy controls of French-Canadian origin. Slow NAT2 acetylation genotype was found to be a significant risk determinant of ALL (odds ratio, 1.5; 95% confidence interval, 1.0-2.2) because of overrepresentation of the alleles NAT2*5C and *7B and underrepresentation of NAT2*4. Besides a slight increase in NAT1*4 allele frequency among cases, no independent association of NAT1 acetylation genotypes and ALL risk was observed. However, the risk associated with NAT2 slow acetylators was more apparent among homozygous individuals for NAT1*4 (odds ratio, 1.9; 95% confidence interval, 1.1-3.4). When NAT2 slow acetylators were considered together with the other risk-elevating genotypes, GSTM1 null and CYP1A1*2A, the risk of ALL increased further, which showed that the combination of these genotypes is more predictive of risk then either of them independently. These findings suggest that leukemogenesis in children is associated with carcinogen metabolism and consequently related to environmental exposures.

Effects of losartan on cerebral arteries in stroke-prone spontaneously hypertensive rats.

OBJECTIVE: To investigate in young salt-loaded stroke-prone spontaneously hypertensive rats (SHR-SP) the effects of a long-term administration of the angiotensin II AT1 receptor antagonist losartan [1 mg/kg (L1) and 10 mg/kg (L10) per day, from 5 to 20 weeks of age] on the structural and functional characteristics of the middle cerebral artery. METHODS: Morphological measurements and isometric tension recordings (myograph, contractile responses to potassium chloride and serotonin, relaxant responses to bradykinin and sodium nitroprusside) were performed on isolated vessels from randomly selected control and losartan-treated SHR-SP and age-matched Wistar-Kyoto (WKY) rats killed at ages 6-7, 10-11 and 16-17 weeks. RESULTS: Whereas all control SHR-SP had died within 18 weeks of being born, losartan at both doses afforded full protection against stroke and mortality. Losartan limited malignant hypertension development dose-dependently. Age-related increases in cerebral arterial wall thickness and wall:lumen ratio were not affected (L1) or limited slightly (L10) by losartan. In control SHR-SP, contractile responses of cerebral arteries to agonists decreased with ageing and stroke occurrence and were significantly smaller than those of age-matched WKY rat arteries. Losartan limited the cerebrovascular contractility impairment dose-dependently in SHR-SP but did not affect the WKY rat cerebral artery contractility. In addition, losartan limited the age-related alteration of the endothelium-dependent relaxation of cerebral arteries observed in control SHR-SP dose-dependently. CONCLUSIONS: In SHR-SP, losartan prevented stroke and improved the cerebral artery's smooth muscle and endothelial cell functions, which are altered during ageing and impaired even more dramatically by stroke occurrence.

Early and late haemodynamic and morphological effects of angiotensin II subtype 1 receptor blockade during genetic hypertension development.

OBJECTIVE: To investigate the haemodynamic and morphological effects resulting from the chronic administration to young spontaneously hypertensive rats (SHR) of a new selective angiotensin II subtype 1 (AT1) receptor antagonist, SR 47436/BMS-186295 (SR/BMS) both during and after the treatment period. METHODS: SR/BMS (60 mg/kg per day, orally) or distilled water was chronically (from 4 to 20 weeks of age) administered to SHR. At age 8, 14, 20 and 28 weeks the effects of SR/BMS on the systemic and regional haemodynamic (radioactive microsphere technique) and the cardiac and vascular morphological parameters (automatic image analysis) were investigated. RESULTS: SR/BMS limited genetic hypertension development and opposed the age-related rises in total peripheral and regional vascular resistances. Simultaneously, it limited the age-related increases in heart weight, left ventricular cross-sectional area and collagen content. Age-related increases in aortic media thickness and amount of collagen were also significantly reduced, whereas aortic compliance was increased. Eight weeks after withdrawal of treatment the antihypertensive effect of SR/BMS, although attenuated, and the limitation of cardiac and vascular remodelling, persisted. CONCLUSIONS: Early AT1 receptor blockade in SHR opposes genetic hypertension development during the treatment period and persistently after its interruption. Prevention of genetic hypertension development during the treatment period can be accounted for by the limitation of the age-related development of the haemodynamic and morphological abnormalities, whereas the persistence of the antihypertensive effect observed after drug withdrawal is due mainly to a maintained prevention of the development of the cardiovascular morphological alterations.

Electron microscopy of gold-labeled human and equine chromosomes.

We present an immunochemical technique for the detection of 5-bromo-2'-deoxyuridine (BrdU) incorporated discontinuously into the chromosomal DNA. A monoclonal anti-BrdU antibody and a protein A-gold complex were used to produce chromosome banding of human and equine chromosomes, specific for electron microscopy (EM). Well-defined bands, symmetry of sister chromatids, concordance between homologues, and band patterns similar to those observed by light microscopy facilitate chromosome identification and karyotyping. From prophase to late metaphase, chromosomes condense and bands appear to fuse. The fusion appears to be owing to chromatin reorganization. Our results underline the value of using immunogold reagents, which are ideal probes for antigen localization on chromosomes.

Systemic and regional hemodynamic profile of five angiotensin I converting enzyme inhibitors in the spontaneously hypertensive rat.

The effects of 5 angiotensin I converting enzyme (ACE) inhibitors--captopril, enalapril, perindopril, trandolapril and ramipril--on general and regional hemodynamics were investigated (using radioactive microspheres) and compared in anesthetized adult spontaneously hypertensive rats. The 5 treatments were administered daily by gavage for 8 days in doses inducing identical decreases in arterial blood pressure. This effect was entirely due to a decrease in total peripheral resistance inasmuch as cardiac index was not affected by the 5 ACE inhibitors. In addition, despite their different chemical structures, all exhibited the same regional vasodilator pattern, which thus appears to be related only to ACE inhibition. The vascular beds resistances were decreased in the following order: renal greater than splenic = liver greater than skin greater than total peripheral greater than muscle = brain. Simultaneously, and despite the decrease in perfusion pressure, most regional blood flows and especially renal blood flow were increased. Finally, renal vasodilator effects of ACE inhibitors were observed even after doses that lacked any effect on total peripheral resistance.

Pharmacokinetics, converting enzyme inhibition and peripheral arterial hemodynamics of ramipril in healthy volunteers.

The effects of a 10 mg dose of ramipril, a new angiotensin I converting enzyme (ACE) inhibitor, on systemic blood pressure, heart rate, brachial artery blood flow, brachial artery diameter, carotid artery blood flow, carotid artery diameter, forearm vascular resistance, plasma ACE and renin activities and plasma aldosterone were investigated. Ramipril's effects in 6 healthy volunteers on a normal sodium diet were compared with those of placebo over a 24-hour period after oral drug intake in an open cross-over trial. Ramipril inhibited plasma ACE activity, an effect that peaked at 3 to 4 hours and persisted up to at least 24 hours. Plasma renin activity increased from 4 to 12 hours after drug intake and plasma aldosterone was slightly decreased. Systemic blood pressure in the supine position was slightly decreased between 6 and 8 hours after drug intake but heart rate remained unaffected. Ramipril significantly increased brachial artery blood flow, brachial artery diameter and carotid artery blood flow and decreased forearm vascular resistance between 3 and 8 hours after drug administration. These peripheral arterial vasodilating effects were more marked in the muscular resistance vessels and affected both large arteries and arterioles in the brachial vascular territory. A correlation was found between the log of plasma concentrations of ramipril diacid metabolite and the drug-induced plasma ACE activity inhibition and increase in brachial artery blood flow. There was also a correlation between these 2 latter effects. A plasma ACE activity inhibition of 80% was required to induce significant increases in brachial artery blood flow and carotid artery blood flow.

Trandolapril's protective effects in stroke-prone spontaneously hypertensive rats persist long after treatment withdrawal.

The effects of long-term oral administration of the angiotensin-converting enzyme (ACE) inhibitor trandolapril (0.01 mg/kg [T0.01] and 1 mg/kg [T1]) on the occurrence of stroke and on mortality were investigated in young salt-loaded stroke-prone spontaneously hypertensive rats during the treatment period (5-20 weeks of age) and up to 8 weeks thereafter. During the treatment period T1, but not T0.01, limited the increase in blood pressure. However, both doses of trandolapril prevented stroke and mortality and strongly opposed (T0.01) or abolished (T1) the increases in saline intake, diuresis, and proteinuria observed in control animals. Simultaneously, trandolapril markedly prevented (T0.01) or abolished (T1) vascular fibrinoid necrosis formation in the brain, kidney, and heart. Finally, trandolapril dose-dependently reduced arterial thickening and glomerular and tubulointerstitial lesions in the kidney, as well as arterial thickening, infarction, and fibrosis in the myocardium. At 8 weeks after treatment withdrawal, the antihypertensive effect of T1 had disappeared, but stroke-related mortality and fibrinoid necrosis remained completely suppressed. Further, no additional cerebral, renal, or cardiac lesions developed, and no increase in proteinuria occurred. In the T0.01 group, 17% of the animals died, fibrinoid necrosis tended to develop, organ lesions worsened, and proteinuria strongly increased. We conclude that (1) early ACE inhibition with trandolapril affords a long-lasting protection versus stroke and mortality both during and after the treatment period; and (2) that this beneficial effect is due to the suppression of fibrinoid necrosis formation and not to the drug's antihypertensive action. In contrast, both properties appear to contribute to trandolapril's renal and cardiac protective effects.