Oxidative status and intestinal health of gilthead sea bream (Sparus aurata) juveniles fed diets with different ARA/EPA/DHA ratios

The present work assessed the effects of dietary ratios of essential fatty acids, arachidonic (ARA), eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), on liver and intestine oxidative status, intestinal histomorphology and gut microbiota of gilthead sea bream. Four isoproteic and isolipidic plant-based diets were formulated containing a vegetable oil blend as the main lipid source. Diets were supplemented with ARA/EPA/DHA levels (%DM) equivalent to: 2%:0.2%:0.1% (Diet A); 1.0%:0.4%:0.4% (Diet B); 0%:0.6%:0.6% (Diet C); 0%:0.3%:1.5% (Diet D) and tested in triplicate groups for 56 days. Lipid peroxidation was higher in fish fed diets C and D while no differences were reported between diets regarding total, oxidized, and reduced glutathione, and oxidative stress index. Glutathione reductase was higher in fish fed diet A than diets C and D. No histological alterations were observed in the distal intestine. Lower microbiota diversity was observed in intestinal mucosa of fish fed diet C than A, while diets C and D enabled the proliferation of health-promoting bacteria from Bacteroidetes phylum (Asinibacterium sp.) and the absence of pathogenic species like Edwardsiella tarda. Overall, results suggest that a balance between dietary ARA/EPA + DHA promotes gilthead sea bream juveniles' health however higher dietary content of n-3 LC-PUFA might limited the presence of microbial pathogens in intestinal mucosa.

Moving Pieces in a Cellular Puzzle: A Cryptic Peptide from the Scorpion Toxin Ts14 Activates AKT and ERK Signaling and Decreases Cardiac Myocyte Contractility via Dephosphorylation of Phospholamban

Cryptic peptides (cryptides) are biologically active peptides formed after proteolysis of native precursors present in animal venoms, for example. Proteolysis is an overlooked post-translational modification that increases venom complexity. The tripeptide KPP (Lys-Pro-Pro) is a peptide encrypted in the C-terminus of Ts14-a 25-mer peptide from the venom of the Tityus serrulatus scorpion that has a positive impact on the cardiovascular system, inducing vasodilation and reducing arterial blood pressure of hypertensive rats among other beneficial effects. A previous study reported that KPP and its native peptide Ts14 act via activation of the bradykinin receptor B2 (B2R). However, the cellular events underlying the activation of B2R by KPP are unknown. To study the cell signaling triggered by the Ts14 cryptide KPP, we incubated cardiac myocytes isolated from C57BL/6 mice with KPP (10^-7 mol·L^-1) for 0, 5, or 30 min and explored the proteome and phosphoproteome. Our results showed that KPP regulated cardiomyocyte proteins associated with, but not limited to, apoptosis, muscle contraction, protein turnover, and the respiratory chain. We also reported that KPP led to AKT phosphorylation, activating AKT and its downstream target nitric oxide synthase. We also observed that KPP led to dephosphorylation of phospholamban (PLN) at its activation sites (S16 and T17), leading to reduced contractility of treated cardiomyocytes. Some cellular targets reported here for KPP (e.g., AKT, PLN, and ERK) have already been reported to protect the cardiac tissue from hypoxia-induced injury. Hence, this study suggests potential beneficial effects of this scorpion cryptide that needs to be further investigated, for example, as a drug lead for cardiac infarction.

Genotoxicity, cytotoxicity and chemical profile from Inga laurina (Fabaceae)

This study aimed to evaluate the cytotoxicity and genotoxicity from Inga laurina leaves extracts and fractions and obtain their chemical profile. The chemical profile of the crude extract from I. laurina leaves and its fractions was investigated through ¹H NMR, RP-HPLC-PDA by co-injection with authentic standards and HPLC-MS. The quinone reductase induction as a biomarker for cancer chemoprevention was evaluated in murine hepatocellular carcinoma line, whereas the cytotoxicity was evaluated by sulforhodamine B assay (SRB) using HepG2 cell line and genotoxicity was evaluated by comet assay. The phytochemical analysis of the leaves crude extract and its fractions showed the presence of 2-hydroxyethyl-dodecanoate and the phenolic compounds: gallic acid, methyl gallate, p-coumaric acid, cinnamic acid, myricetin-3-O-(2″-O-galoyl)-α-rhamnopyranoside, proanthocyanidin A-2 and myricetrin. All the fractions tested were not considered cytotoxic against the selected human cancer cell lines, they did not cause genotoxic in some concentrations damage and induced the enzyme quinone reductase.

Moving pieces in a cryptomic puzzle: Cryptide from Tityus serrulatus Ts3 Nav toxin as potential agonist of muscarinic receptors

Cryptome is as a subset of a given proteome containing bioactive cryptides embedded in larger peptides or proteins. We pinpointed a striking sequence similarity between two peptides from the Tityus serrulatus venom: Ts10 (KKDGYPVEYDRAY) and the N-terminal of Ts3 (KKDGYPVEYDNCAY). Ts3 (former Tityustoxin or TsIV) is an α-neurotoxin acting on voltage-gated sodium channels while Ts10 (former Peptide T) is a bradykinin-potentiating peptide and was originally reported as inhibitor of the angiotensin-converting enzyme (ACEi). Thus, the goal of this study was to evaluate whether such peptide hidden in the N-terminal of Ts3 (Ts3_1-14[C12S]) was able to mimic known effects of Ts10 as well as to expand the current knowledge of the vascular effects and molecular targets of these peptides. Similar to Ts10, Ts3_1-14[C12S] was able to potentiate the hypotensive effect of bradykinin (BK). However, none of these peptides was able to induce a long-lasting BK-potentiating effect, suggesting that this effect may not be their main biological outcome. On the other hand, we report that Ts10 and mainly Ts3_1-14[C12S] induced a strong vasodilation effect depending on the presence of functional endothelium and nitric oxide (NO) production. Unlike previously reported, Ts10 was not able to inhibit ACE activity (similar result was observed for Ts3_1-14[C12S]). On the other hand, we report that Ts3_1-14[C12S] induces vasodilation via the activation of muscarinic acetylcholine receptors (mAChRs) M2 and M3 while only the activation of mAChR M2 seems to be required for Ts10-induced vasodilation.

Effects of lipoic acid on growth and biochemical responses of common carp fed with carbohydrate diets

Lipoic acid (LA) is an antioxidant that also favors glucose uptake in mammals. Until now, there are no studies evaluating the potential effect of this molecule on glycemic control in fish. It was evaluated LA effects on glucose uptake in common carp Cyprinus carpio fed with carbohydrate diets from two carbohydrate sources: glucose (GLU) and starch (STA), and supplemented or not with LA, being the diets: +GLU/-LA (GLU); +GLU/+LA (GLU + LA); +STA/-LA (STA); and +STA/+LA (STA + LA). Carp juveniles (6.5 ± 0.1 g) were fed with each diet ad libitum 4 times a day, during 68 days. Muscle glycogen concentration was higher (p < 0.05) in GLU and GLU + LA than in STA and STA + LA groups. On fish fed with starch, muscle cholesterol and triglyceride concentrations were higher (p < 0.05) in fish fed diets supplemented with LA. Muscle protein levels were higher in fish fed with LA, independent of the diet carbohydrate source. Lipid peroxidation was significantly reduced (p < 0.05) in fish muscle on fish fed the STA + LA diets when compared with the STA diet. Our findings indicate that LA modulates lipid, proteins and carbohydrate metabolism together with the well-known antioxidant effect. Also, LA showed to enhance starch utilization taking into account muscle cholesterol and triglyceride levels.

Therapeutic uses for Angiotensin-(1-7)

INTRODUCTION

Angiotensin-(1-7) is a key component of the Renin-Angiotensin System, which can counter-regulate several deleterious effects caused by angiotensin II. Due to the potential for therapeutic use, several of its actions are specifically described in patents.

AREAS COVERED

In this review, the authors describe a plethora of therapeutic uses for Angiotensin-(1-7), claimed and supported by experimental evidence in patent documents and applications.

EXPERT OPINION

The clinical potential of Angiotensin-(1-7) as a therapeutic agent to treat several pathologies is evidenced by the variety of patents and clinical trials involving this peptide. Cancer treatment is one of the most advanced therapeutic areas, but clinical studies are also available in several other areas, such as cardiovascular, hematological, transplantation, surgical and medical procedures.

Effect of l-glutamic acid supplementation on performance and nitrogen balance of broilers fed low protein diets

The aim of this study was to evaluate the effect of protein reduction and supplementation of l-glutamic acid in male broiler diets. A total of 648 chicks of the Cobb 500 strain were distributed in a completely randomized design with six treatments and six replications with eighteen birds per experimental unit. The study comprised pre-starter (1-7 days), starter (8-21 days), growth (22-35 days) and final (36-45 days) phases. The first treatment consisted of a control diet formulated according to the requirements of essential amino acids for each rearing phase. The second and third treatments had crude protein (CP) reduced by 1.8 and 3.6 percentage points (pp) in relation to the control diet respectively. In the fourth treatment, l-glutamic acid was added to provide the same glutamate level as the control diet, and in the last two treatments, the broilers were supplemented with 1 and 2 pp of glutamate above that of the control diet respectively. The reduction in CP decreased the performance of broilers and the supplementation of l-glutamic acid did not influence performance when supplied in the diets with excess of glutamate. The lowest excreted nitrogen values were observed in the control diet, and treatments 2 and 3, respectively, in comparison with treatments with the use of l-glutamic acid (5 and 6). Retention efficiency of nitrogen was better in the control diet and in the treatment with a reduction of 1.8 pp of CP. It was verified that the serum uric acid level decreased with the CP reduction. A reduction in CP levels of up to 21.3%, 18.8%, 18.32% and 17.57% is recommended in phases from 1 to 7, 8 to 21, 22 to 35 and at 36 to 42 days, respectively, with a level of glutamate at 5.32%, 4.73%, 4.57%, 4.38%, also in these phases.

HLA alleles and HLA-B27 haplotypes associated with susceptibility and severity of ankylosing spondylitis in a Portuguese population

Human leukocyte antigen (HLA)-B27 is the mostly known major histocompatibility complex (MHC) gene associated with ankylosing spondylitis (AS). Nonetheless, there is substantial evidence that other MHC genes appear to be associated with the disease, although it has not yet been established whether these associations are driven by direct associations or by linkage disequilibrium (LD) mechanisms. We aimed to investigate the contributions of HLA class I and II alleles and B27-haplotypes for AS in a case-control study. A total of 188 HLA-B27 AS cases and 189 HLA-B27 healthy controls were selected and typed for HLA class I and II by the Luminex polymerase chain reaction-sequence specific oligonucleotide probe (PCR-SSOP) method. Allelic and haplotypic distributions were estimated by maximum likelihood method using Arlequin v3.11 and statistical analysis were performed by Stata10.1. No associations were found between non-HLA-B27 loci and AS susceptibility, but several associations were observed for phenotypic features of the disease. DRB1*08 was identified as a risk factor for uveitis and DQB1*04 seems to provide protection for AS severity (functional, metrological and radiological indexes). A*02/B27/C*02/DRB1*01/DQB1*05 [P<0.0001; odds ratio (OR) = 39.06; 95% confidence interval (CI) (2.34-651)] is the only haplotype that seems to confer susceptibility to AS. Moreover, the haplotype A*02/B27/C*01/DRB1*08/DQB1*04 seems to provide protection for disease functional and radiological repercussions. Our findings are compatible with the hypothesis that other genes within the HLA region besides HLA-B27 might play some role in AS susceptibility and severity.

The effect of osteoarthritis definition on prevalence and incidence estimates: a systematic review

OBJECTIVE

To understand the differences in prevalence and incidence estimates of osteoarthritis (OA), according to case definition, in knee, hip and hand joints.

METHOD

A systematic review was carried out in PUBMED and SCOPUS databases comprising the date of publication period from January 1995 to February 2011. We attempted to summarise data on the incidence and prevalence of OA according to different methods of assessment: self-reported, radiographic and symptomatic OA (clinical plus radiographic). Prevalence estimates were combined through meta-analysis and between-study heterogeneity was quantified.

RESULTS

Seventy-two papers were reviewed (nine on incidence and 63 on prevalence). Higher OA prevalences are seen when radiographic OA definition was used for all age groups. Prevalence meta-analysis showed high heterogeneity between studies even in each specific joint and using the same OA definition. Although the knee is the most studied joint, the highest OA prevalence estimates were found in hand joints. OA of the knee tends to be more prevalent in women than in men independently of the OA definition used, but no gender differences were found in hip and hand OA. Insufficient data for incidence studies didn't allow us to make any comparison according to joint site or OA definition.

CONCLUSIONS

Radiographic case definition of OA presented the highest prevalences. Within each joint site, self-reported and symptomatic OA definitions appear to present similar estimates. The high heterogeneity found in the studies limited further conclusions.

Kawasaki disease and human bocavirus--potential association?

Kawasaki disease (KD) is an acute febrile multisystem vasculitic syndrome of unknown etiology, occurring mostly in infants and children younger than 5 years of age. We present a 13-month-old male with KD from whom was found human bocavirus DNA in nasopharyngeal secretions. Human bocavirus DNA in a patient with KD raised question about the coincidental or possible etiological association.

The influence of improved glycaemic control with chlorpropamide on microvascular reactivity and nitric oxide synthase activity in diabetic rats

Hyperglycaemia is a primary cause of vascular complications in diabetes. A hallmark of these vascular complications is endothelial cell dysfunction, which is partly due to reduced production of nitric oxide. The aim of this study was to verify the influence of improved glycaemic control with chlorpropamide on microvascular reactivity, endothelial nitric oxide synthase (e-NOS) expression, and NOS activity in neonatal streptozotocin-induced diabetic rats (n-STZ). Diabetes was induced by STZ injection into neonates Wistar rats. n-STZ diabetic rats were treated with chlorpropamide (200 mg kg−1, 15 days, by gavage). The changes in mesenteric arteriolar and venular diameters were determined in anaesthetized control and n-STZ diabetic rats, before and after topical application of acetylcholine, bradykinin and sodium nitroprusside (SNP). We also assessed e-NOS expression (using polymerase chain reaction after reverse transcription of mRNAs into cDNAs) and NOS activity (conversion of L-arginine to citrulline) in the mesenteric vascular bed of chlorpropamide-treated n-STZ, vehicle-treated n-STZ, and control rats. In n-STZ, chlorpropamide treatment reduced high glycaemic levels, improved glucose tolerance and homoeostatic model assessment (HOMA-beta), and restored NOS activity. Impaired vasodilator responses of arterioles and venules to acetylcholine, bradykinin and SNP were partially corrected by chlorpropamide treatment in n-STZ. We concluded that improved metabolic control and restored NOS activity might be collaborating with improved microvascular reactivity found in chlorpropamide-treated n-STZ.

The vasoactive peptide angiotensin-(1-7), its receptor Mas and the angiotensin-converting enzyme type 2 are expressed in the human endometrium

Angiotensin (Ang)-(1-7) is one of the major active components of the renin-angiotensin system, produced from cleavage of Ang II by angiotensin-converting-enzyme type 2 (ACE2), which acts through a specific G protein-coupled receptor, Mas. We have investigated whether the human endometrium expresses these components during menstrual cycle. By radioimmunoassay, Ang-(1-7) was detected in endometrial wash fluid at picomolar concentrations. Using immunofluorescence, both the peptide and its receptor were identified in cultured endometrial epithelial and stromal cells. By immunohistochemistry, Ang(1-7) was localized in the endometrium throughout menstrual cycle, being more concentrated in the glandular epithelium of mid- and late secretory phase. This pattern corresponded to the ACE2 mRNA, which was more abundant in epithelial cells than in stromal cells (2-fold increase, p < 0.05) and in the secretory vs. proliferative phase (6.6-fold increase, p < 0.01). The receptor Mas was equally distributed between epithelial and stromal cells and did not change during menstrual cycle. The physiological role of this peptide system in normal and pathological endometrium warrants further investigation.

Cytotoxic and genotoxic monitoring of sickle cell anaemia patients treated with hydroxyurea

Very satisfactory results have been obtained with the treatment of sickle cell anaemia with hydroxyurea (HU), an antineoplastic drug. This is because it significantly increases the levels of foetal haemoglobin. Nevertheless, inadequate dosages or prolonged treatment with this pharmaceutical can provoke cytotoxicity or genotoxicity, increasing the risk of neoplasia. We monitored patients under treatment with HU for possible mutagenic effects, through cytogenetic tests (mitotic index and chromosome aberrations) for one year. Checking at two-month intervals, the cytotoxic effect was not evident. There was no evidence of genotoxicity under the conditions of our experiment. However individuals treated with HU should be constantly monitored, as an absence of genotoxicity could be transitory; the mitotic index should also be observed, as an indicator of cytotoxicity.

Genotoxic effects of aluminum chloride in cultured human lymphocytes treated in different phases of cell cycle

Aluminum (Al) is the most abundant metal and the third common chemical element on earth. It is known that Al is toxic, especially its trivalent form (Al(3+)), that represents the its most soluble form. Al intoxication is related to some pathogenic disorders, principally neurodegeneratives ones as Parkinson and Alzheimer diseases. The present study aimed to evaluate the mutagenic potential of aluminum chloride (AlCl(3)). Comet assay and chromosome aberrations analysis were applied to evaluate the DNA-damaging and clastogenic effects of AlCl(3), respectively, in different phases of the cell cycle. Cultured human lymphocytes were treated with 5, 10, 15 and 25 microM aluminum chloride during the G1, G1/S, S (pulses of 1 and 6h), and G2 phases of the cell cycle. All tested concentrations were cytotoxic and reduced significantly the mitotic index in all phases of cell cycle. They also induced DNA damage and were clastogenic in all phases of cell cycle, specially in S phase. AlCl(3) also induced endoreduplication and polyploidy in treatments performed during G1 phase. The presence of genotoxicity and polyploidy on interphase and mitosis, respectively, suggests that aluminum chloride is clastogenic and indirectly affects the construction of mitotic fuse in all tested concentrations.

Cardiac angiotensin II type I and type II receptors are increased in rats submitted to experimental hypothyroidism

This study assessed the behaviour of angiotensin II (Ang II) receptors in an experimental hypothyroidism model in male Wistar rats. Animals were subjected to thyroidectomy and resting for 14 days. The alteration of cardiac mass was evaluated by total heart weight (HW), right ventricle weight (RVW), left ventricle weight (LVW), ratio of HW, RVW and LVW to body weight (BW) and atrial natriuretic factor (ANF) expression. Cardiac and plasma Ang II levels and serum T3 and T4 were determined. The mRNA and protein levels of Ang II receptors were investigated by RT-PCR and Western blotting, respectively. Functional analyses were performed using binding assays. T3 and T4 levels and the haemodynamic parameters confirmed the hypothyroid state. HW/BW, RVW/BW and LVW/BW ratios and the ANF expression were lower than those of control animals. No change was observed in cardiac or plasma Ang II levels. Both AT1/AT2 mRNA and protein levels were increased in the heart of hypothyroid animals due to a significant increase of these receptors in the RV. Experiments performed in cardiomyocytes showed a direct effect promoted by low thyroid hormone levels upon AT1 and AT2 receptors, discarding possible influence of haemodynamic parameters. Functional assays showed that both receptors are able to bind Ang II. Herein, we have identified, for the first time, a close and direct relation of elevated Ang II receptor levels in hypothyroidism. Whether the increase in these receptors in hypothyroidism is an alternative mechanism to compensate the atrophic state of heart or whether it may represent a potential means to the progression of heart failure remains unknown.

Use of Hyperbaric Oxygenation in Small Bowel Preservation for Transplant

INTRODUCTION

The aim of this work was to study the effects of hyperbaric oxygenation as a preservation technique for small bowel transplantation.

METHODS

Twenty 2-month-old male Wistar rats weighting 250 g were divided into two groups: group A (n = 10) in which the small bowel was preserved for 12 hours, and group B (n = 10) in which the small bowel was preserved for 24 hours. After vascular and intraluminal perfusion, 3-cm segments were maintained in Ringer's solution at temperatures between 2 degrees C to 4 degrees C and in normobaric O2 conditions (groups A1, B1) or conditioned in an hyperbaric O2 metal chamber (100% oxygen at 5.5 absolute atmospheres) (groups A2, B2). After this preservation time, we studied intestinal tissue injury and morphometric analysis of the villi.

RESULTS

Mucosal injury was significantly greater among group A1 compared to group A2 animals. The grade of the lesions was greater among group B1 compared to group B2 animals. Group A1 showed no difference from Group B1. For lesion grade, the range was smaller in group A2 and group B2 animals. The villi height was significantly smaller in groups A1 and B1 compared to the other groups; whereas it was higher in group A2 as compared with B2.

CONCLUSION

Hyperbaric oxygenation may play a role as a preservation technique. Further research is necessary.

A Novel System for Organ and Tissues Preservation: The Refrigerating Hyperbaric Chamber

This study was designed to investigate the feasibility of building a simple and inexpensive device to preserve organs or tissues in hyperbaric and hypothermic conditions.

METHODS

The device was built on a 40-cm wide, 28-cm long, and 23-cm deep stainless steel chassis. The pressure vessel was built by a 7.8-cm bore stainless steel cylinder put inside another 12-cm cylinder welded together and closed by a steel plate on the top and bottom. The inferior plate was welded, and the superior one was fixed by manual clasp nut. The cooling system is made up of air compressor, condenser, expansion area, and cooling worm that is located between the cylinders. The temperature-controlling device is a computer processor contained in an integrated-circuit chip, with a on-off system to maintain the chamber temperature between 2 degrees to 4 degrees C. The compression of the chamber is performed by lateral coupling with the oxygen cylinder and is maintained at 5.5 absolute atmospheres and controlled by air pressure gauge. The maximal work pressure was evaluated by spreadsheet. Temperature or pressure changes were evaluated by 12- and 24-hour assays.

RESULTS

The maximal work pressure permitted was 6.5 absolute atmospheres. Thus, the container was free from danger. The temperature inside the chamber was kept between 2 degrees and 4 degrees C. The production costs of the prototype was US$1000.

DISCUSSION

The manufacture of the refrigerating hyperbaric chamber is viable, simple, and inexpensive.

Apoptosis and Nuclear Proliferation in Rat Small Bowel Submitted to Hypothermic Hyperbaric Oxygenation for Preservation

This study was conducted to assess apoptosis and nuclear proliferation in rat small bowel submitted to hypothermic hyperbaric oxygenation for preservation.

METHODS

Twenty two-month-old, male Wistar rats, weighing 250 g were divided into two groups: group I (n = 10), in which the small bowel was preserved for 12 hours, and group II (n = 10) in which the small bowel was preserved for 24 hours. After vascular and intraluminal perfusion, 3-cm segments were maintained in Ringer's solution at 2 degrees to 4 degrees C under normobaric conditions (groups Ia and IIa) or conditioned in a small hyperbaric metal chamber with 100% oxygen at 5.5 absolute atmospheres (groups Ib and IIb). After 12 or 24 hours, apoptotic and mitotic indices were evaluated by immunohistochemical methods.

RESULTS

The apoptotic index was significantly higher in small bowel segments in groups Ia and IIa compared with groups Ib and IIb. The mitotic index was significantly higher among group IIb.

CONCLUSION

Hypothermic hyperbaric oxygenation reduced intestinal epithelial apoptosis and increased nuclear proliferation during rat small bowel preservation.

Long-lasting cardiovascular effects of liposome-entrapped angiotensin-(1-7) at the rostral ventrolateral medulla

The aim of this work was to evaluate the potential of liposomes as a tool for the sustained release of the short half-life peptides of the renin-angiotensin system in a specific site of the brain. Angiotensin (Ang)-(1-7) was selected for this study because of its known cardiovascular effects at the level of the rostral ventrolateral medulla (RVLM) and because of the considerable interests in elucidating its physiopathological role as a neuromodulator. Ang-(1-7)-containing liposomes (LAng) were microinjected unilaterally in the RVLM of Wistar rats, and the effects on blood pressure (MAP) and heart rate were evaluated by telemetry. Empty liposomes (Lemp) were used as control. LAng elicited a significant pressor effect during daytime and bradycardia during nighttime that lasted for 5 and 3 days, respectively. These cardiovascular effects resulted in a significant attenuation of the circadian variations of MAP and heart rate. In the case of MAP, a significant inversion of the circadian rhythm was observed on day 2 after LAng microinjection. None of these effects were observed following microinjection of Lemp. Using this novel technique, it was possible to establish, in chronic conditions, the pressor effect of Ang-(1-7) at the RVLM. Moreover, our data unmasks a new physiological role for Ang-(1-7) at the level of the RVLM: modulation of the circadian rhythms of MAP and heart rate.

Angiotensin-(1-7): cardioprotective effect in myocardial ischemia/reperfusion

In this study we evaluate the effects of angiotensin-(1-7) on reperfusion arrhythmias in isolated rat hearts. Rat hearts were perfused according to Langendorff technique and maintained in heated (37+/-1 degrees C) and continuously gassed (95% O(2)/5% CO(2)) Krebs-Ringer solution at constant pressure (65 mm Hg). The electrical activity was recorded with an ECG (bipolar). Local ischemia was induced by coronary ligation for 15 minutes. After ischemia, hearts were reperfused for 30 minutes. Cardiac arrhythmias were defined as the presence of ventricular tachycardia and/or ventricular fibrillation after the ligation of the coronary artery was released. Angiotensin II (0.20 nmol/L, n=10) produced a significant enhancement of reperfusion arrhythmias. On the other hand, Ang-(1-7) presented in the perfusion solution (0.22 nmol/L, n=11) reduced incidence and duration of arrhythmias. The antiarrhythmogenic effects of Ang-(1-7) was blocked by the selective Ang-(1-7) antagonist A-779 (2 nmol/L, n=9) and by indomethacin pretreatment (5 mg/kg IP, n=8) but not by the bradykinin B(2) antagonist HOE 140 (100 nmol/L, n=10) or by L-NAME pretreatment (30 mg/kg IP, n=8). These results suggest that the antiarrhythmogenic effect of low concentrations of Ang-(1-7) is mediated by a specific receptor and that release of endogenous prostaglandins.by Ang-(1-7) contributes to the alleviation of reversible and/or irreversible ischemia-reperfusion injury.

Baroreflex improvement in shr after ace inhibition involves angiotensin-(1-7)

ACE inhibitors are extensively used in the treatment of hypertension mainly because of their efficiency in reducing blood pressure levels and decreasing vascular and cardiac hypertrophy. In addition, ACE inhibitors improve baroreceptor reflex control. Chronic inhibition of ACE produces (in addition to decreased angiotensin II levels) a severe increase in angiotensin-(1-7) [Ang-(1-7)] levels in several species. We have previously shown that Ang-(1-7) produces a facilitation of the baroreflex control of heart rate. In this study, we evaluated the participation of endogenous Ang-(1-7) in the improvement of baroreflex sensitivity in spontaneously hypertensive rats after central infusion of ramiprilat, an ACE inhibitor. Reflex changes in heart rate were elicited, in conscious rats, by bolus injections of phenylephrine (baroreflex bradycardia) before and after intracerebroventricular infusion of (1) saline (8 microL/h), 4 hours (n=5); (2) ramiprilat (14 microg/h), 4 hours (n=6); (3) ramiprilat for 2 hours, followed by ramiprilat combined with A-779 (4 microg/h), a selective Ang-(1-7) antagonist, for an additional 2 hours (n=6); and (4) A-779 for 2 hours, followed by A-779 combined with ramiprilat for an additional 2 hours (n=5). Intracerebroventricular infusion of ramiprilat produced an important increase ( approximately 40%) in baroreflex sensitivity (evaluated as the ratio between changes in heart rate and changes in mean arterial pressure) that was completely reversed by A-779. Furthermore, intracerebroventricular infusion of A-779 prevented the improvement of the baroreflex sensitivity produced by ramiprilat. Intracerebroventricular infusion of saline or A-779 alone did not significantly alter the baroreflex sensitivity. These results suggest that endogenous Ang-(1-7) is involved in the improvement of baroreflex sensitivity observed in spontaneously hypertensive rats during central ACE inhibition.

Mechanisms of angiotensin-(1-7)-induced inhibition of angiogenesis

Angiotensin-(1-7) [ANG-(1-7)], an endogenous bioactive peptide constituent of the renin-angiotensin system, acts as an inhibitory growth factor in vitro and in vivo. In this study, we evaluated whether the antiangiogenic effect of ANG-(1-7) in the mouse sponge model of angiogenesis might be receptor mediated and involved in the release of nitric oxide (NO). The hemoglobin content (microg/mg wet tissue) of 7-day-old sponge implants was used as an index of the vascularization and showed that daily injections of ANG-(1-7) (20 ng) inhibited significantly the angiogenesis in the implants relative to the saline-treated group. The specific receptor antagonist D-Ala(7)-ANG-(1-7); A-779 prevented ANG-(1-7)-induced inhibition of angiogenesis. The antiangiogenic effect was also abolished by pretreatment with NO synthase inhibitors aminoguanidine (1 mg/ml) or N(G)-nitro-L-arginine methyl ester (0.3 mg/ml). Selective AT1 and AT2 angiotensin-receptor antagonists and an angiotensin-converting enzyme inhibitor, in combination with ANG-(1-7) or alone, did not alter angiogenesis in the implants. These results establish that the regulation of the vascular tissue growth by ANG-(1-7) is associated with NO release by activation of an angiotensin receptor distinct from AT1 and AT2.

The influence of ultrasound on the retention of cast posts cemented with different agents

AIM

The aim of this study was to evaluate the influence of ultrasound during the removal of posts cemented with either zinc phosphate cement, glass ionomer cement or resin cement.

METHODOLOGY

Eighty-four single-rooted teeth were prepared and after cementation of cast posts, they were randomly divided into six groups of 14. Group 1, 2 and 3 did not receive ultrasonic vibration, whilst groups 4, 5 and 6 received ultrasonic vibration for 10 min. The force necessary for post removal was determined using a universal testing machine. Results were statistically analysed using ANOVA and Tukey tests (5%).

RESULTS

The application of ultrasonic vibration reduced the retention provided by zinc phosphate and glass ionomer cements by 39% and 33%, respectively.

CONCLUSIONS

A statistically significant reduction in the force necessary to remove posts cemented with zinc phosphate and glass ionomer cements occurred following application of ultrasound. The application of ultrasonic vibration did not influence the retention of cast posts cemented with resin cement.

Alterations of the renin-angiotensin system at the RVLM of transgenic rats with low brain angiotensinogen

The transgenic rats TGR(ASrAOGEN) (TGR) with low levels of brain angiotensinogen were analyzed for cardiovascular reactivity to microinjections of ANG II and angiotensin receptor (AT(1)) antagonists [CV-11974, AT(1) specific; A-779, ANG-(1--7) selective; sarthran, nonspecific] into the rostral ventrolateral medulla (RVLM) of conscious rats. Microinjection of ANG II resulted in a significantly higher increase in the mean arterial pressure (MAP) of TGR than control [Sprague-Dawley (SD)] rats, suggesting an upregulation of ANG II receptors in TGR. CV-11974 produced an increase in MAP of SD but not in TGR rats. A-779 produced a depressor response in SD but not in TGR rats. Conversely, sarthran produced a similar decrease of MAP in both rat groups. The pressor effect of the AT(1) antagonist may indicate an inhibitory role of AT(1) receptors in the RVLM. On the other hand, ANG-(1--7) appears to have a tonic excitatory role in this region. The altered response to specific angiotensin antagonists in TGR further supports the functionally relevant decrease in angiotensins in the brains of TGR and corroborates the importance of the central renin-angiotensin system in cardiovascular homeostasis.

Potentiation of bradykinin by angiotensin-(1-7) on arterioles of spontaneously hypertensive rats studied in vivo

In the present study, we investigated the potentiating effect of angiotensin-(1-7) [Ang-(1-7)] on bradykinin (BK)-induced vasodilation in the mesenteric vascular bed of anesthetized spontaneously hypertensive rats using intravital microscopy. Topical application of BK and Ang-(1-7) induced vasodilation in mesenteric arterioles. The BK-induced effect, but not acetylcholine, sodium nitroprusside, or histamine responses, was potentiated in the presence of Ang-(1-7). This interaction was abolished by BK-B(2) and Ang-(1-7) antagonists (HOE 140 and A-779, respectively), a K(+) channel blocker (tetraethylammonium), and cyclooxygenase inhibitors (indomethacin and diclofenac); however, nitric oxide synthase inhibition (Nomega-nitro-L-arginine methyl ester) did not modify the Ang-(1-7)-potentiating activity. Long-term angiotensin-converting enzyme (ACE) inhibition increased BK and Ang-(1-7)-induced vasodilation. The BK potentiation by Ang-(1-7) was preserved after ACE inhibition, Ang II type 1 receptor blockade, or the combination of both treatments. The most striking finding of this study was the unexpected observation that the potentiation of BK vasodilation in spontaneously hypertensive rats treated short- or long-term with ACE inhibitors was reverted by the Ang-(1-7) antagonist A-779. Our results unmasked a key role for an Ang-(1-7)-related mechanism in mediating BK potentiation by ACE inhibitors.

Modulation of the baroreflex control of heart rate by angiotensin-(1-7) at the nucleus tractus solitarii of normotensive and spontaneously hypertensive rats

OBJECTIVES

In the present study, we evaluated the effect of angiotensin-(1-7) [Ang-(1-7)] and its selective antagonist, D-Ala7-Ang-(1-7) (A-779), at the nucleus tractus solitarii (nTS), in the modulation of the bradycardic component of the baroreceptor reflex.

METHODS

Mean arterial pressure (MAP) and heart rate were continuously recorded. Reflex changes in heart rate elicited by bolus injection of graded doses of phenylephrine were evaluated before and after bilateral microinjection (glass micropipette) of Ang-(1-7) (10 pmol or 25 pmol), A-779 (50 pmol) or saline (vehicle) into the nTS of urethane anesthetized male Wistar rats or spontaneously hypertensive rats (SHR). The averaged ratio between reflex changes in heart rate and changes in MAP was used as index of baroreflex sensitivity.

RESULTS

Microinjection of Ang-(1-7) into the nTS elicited significant decreases in MAP and heart rate in both Wistar and SHR. While the decrease in MAP was similar in both strains, the changes in heart rate were smaller in SHR. A-779 produced small changes in MAP and heart rate that were no different from those induced by saline. After microinjection of 10 pmol of Ang-(1-7) into the nTS of normotensive rats, there was a significant increase in baroreflex sensitivity. In SHR, only the microinjection of a higher dose (25 pmol) of Ang-(1-7) produced a significant increase in baroreflex sensitivity. A significant reduction inbaroreflex sensitivity was observed after microinjection of A-779 (50 pmol) in both strains.

CONCLUSIONS

These results indicate that Ang-(1-7) exerts a tonic modulatory effect on the baroreflex control of heart rate at the nTS, probably through a non-AT1 non-AT2 receptor subtype. In addition, our data showed a reduced sensitivity to Ang-(1-7) at the nTS of SHR, that could be accounting, at least in part, for the decreased baroreflex sensitivity present in this model of hypertension.

Angiotensin-(1-7) regulates the levels of angiotensin II receptor subtype AT1 mRNA differentially in a strain-specific fashion

Ang-(1-7) is an effector peptide of the renin-angiotensin system with several distinct actions that are likely mediated by a specific receptor. Regulatory effects of angiotensin (Ang) peptides, Ang-(1-7) and Ang II, on Ang receptor subtype 1 (AT1) mRNA expression were investigated in vascular smooth muscle cells (VSMC) from four University of Akron (Akr) rat strains (WKY, SHR and two backcross consomic lines SHR/y and SHR/a), and in SHR and WKY cells from Charles River Laboratories (Crl). In WKY/Akr and SHR/Akr, Ang-(1-7) treatment increased the levels of AT1 mRNA. This effect was inhibited by the specific Ang-(1-7) antagonist, A-779, in WKY/Akr but not SHR/Akr. Ang II had no effect in Akr cells, but it down-regulated AT1 mRNA in WKY/Crl and SHR/Crl VSMC. Ang-(1-7) did not affect AT1 mRNA levels in Crl lines. In conclusion, Ang-(1-7) regulates the AT1 receptor either directly or indirectly in a strain-specific fashion. The Ang-(1-7) antagonist, A-779, blocks the actions of Ang-(1-7) only in VSMC from WKY/Akr rats, suggesting either that the binding sites for Ang-(1-7) have different properties in SHR/Akr and WKY/Akr cell lines, or that some of the effects of Ang-(1-7) are not receptor mediated. Further, we found differences between Akr cells and Crl cells that are consistent with their genetic heterogeneity.

Varicella-zoster virus gE escape mutant VZV-MSP exhibits an accelerated cell-to-cell spread phenotype in both infected cell cultures and SCID-hu mice

Varicella-zoster virus is considered to have one of the most stable genomes of all human herpesviruses. In 1998, we reported the unanticipated discovery of a wild-type virus that had lost an immunodominant B-cell epitope on the gE ectodomain (VZV-MSP); the gE escape mutant virus exhibited an unusual pattern of egress. Further studies have now documented a markedly enhanced cell-to-cell spread by the mutant virus in cell culture. This property was investigated by laser scanning confocal microscopy combined with a software program that allows the measurement of pixel intensity of the fluorescent signal. For this new application of imaging technology, the VZV immediate early protein 62 (IE 62) was selected as the fluoresceinated marker. By 48 h postinfection, the number of IE 62-positive pixels in the VZV-MSP-infected culture was nearly fourfold greater than the number of pixels in a culture infected with a low-passage laboratory strain. Titrations by infectious center assays supported the above image analysis data. Confirmatory studies in the SCID-hu mouse documented that VZV-MSP spread more rapidly than other VZV strains in human fetal skin implants. Generally, the cytopathology and vesicle formation produced by other strains at 21 days postinfection were demonstrable with VZV-MSP at 14 days. To assess whether additional genes were contributing to the unusual VZV-MSP phenotype, approximately 20 kb of the VZV-MSP genome was sequenced, including ORFs 31 (gB), 37 (gH), 47, 60 (gL), 61, 62 (IE 62), 66, 67 (gI), and 68 (gE). Except for a few polymorphisms, as well as the previously discovered mutation within gE, the nucleotide sequences within most open reading frames were identical to the prototype VZV-Dumas strain. In short, VZV-MSP represents a novel variant virus with a distinguishable phenotype demonstrable in both infected cell cultures and SCID-hu mice.

Angiotensin-(1-7): an update

The renin-angiotensin system is a major physiological regulator of arterial pressure and hydro-electrolyte balance. Evidence has now been accumulated that in addition to angiotensin (Ang) II other Ang peptides [Ang III, Ang IV and Ang-(1-7)], formed in the limited proteolysis processing of angiotensinogen, are importantly involved in mediating several actions of the RAS. In this article we will review our knowledge of the biological actions of Ang-(1-7) with focus on the puzzling aspects of the mediation of its effects and the interaction Ang-(1-7)-kinins. In addition, we will attempt to summarize the evidence that Ang-(1-7) takes an important part of the mechanisms aimed to counteract the vasoconstrictor and proliferative effects of Ang II.

Standardization of a fluorimetric assay for the determination of tissue angiotensin-converting enzyme activity in rats

The tripeptide Hip-His-Leu was used to standardize a fluorimetric method to measure tissue angiotensin-converting enzyme (ACE) activity in rats. The fluorescence of the o-phthaldialdehyde-His-Leu adduct was compared in the presence and absence of the homogenate (25 microl) to determine whether the homogenate from different tissues interfered with the fluorimetric determination of the His-Leu product. Only homogenates from lung and renal medulla and cortex showed significantly altered fluorescence intensity. To overcome this problem, the homogenate from these tissues were diluted 10 times with assay buffer. The specificity of the assay was demonstrated by the inhibition of ACE activity with 3 microM enalaprilat (MK-422). There was a linear relationship between product formation and incubation time for up to 90 min for homogenates of renal cortex and medulla and liver, for up to 60 min for ventricles and adrenals and for up to 30 min for the aorta, lung and atrium homogenates. In addition, there was a linear relationship between product formation and the amount of protein in the homogenates within the following range: lung, 30-600 microg; renal cortex and medulla, 40-400 microg; atrium and ventricles, 20-200 microg; adrenal, 20-100 microg; aorta, 5-100 microg; liver, 5-25 microg. No peptidase activity against the His-Leu product (31 nmol), assayed in borate buffer (BB), was detected in the different homogenates except the liver homogenate, which was inhibited by 0.1 mM rho-chloromercuribenzoic acid. ACE activity in BB was higher than in phosphate buffer (PB) due, at least in part, to a greater hydrolysis of the His-Leu product in PB. ACE activity of lung increased 20% when BB plus Triton was used. Enzyme activity was stable when the homogenates were stored at -20o or -70oC for at least 30 days. These results indicate a condition whereby ACE activity can be easily and efficiently assayed in rat tissue samples homogenized in BB using a fluorimetric method with Hip-His-Leu as a substrate.

Angiotensin-(1-7) potentiates the coronary vasodilatatory effect of bradykinin in the isolated rat heart

It has been shown that angiotensin-(1-7) (Ang-(1-7)) infusion potentiates the bradykinin (BK)-induced hypotensive response in conscious rats. The present study was conducted to identify Ang-(1-7)-BK interactions in the isolated rat heart perfused according to the Langendorff technique. Hearts were excised and perfused through the aortic stump under a constant flow with Krebs-Ringer solution and the changes in perfusion pressure and heart contractile force were recorded. Bolus injections of BK (2.5, 5, 10 and 20 ng) produced a dose-dependent hypotensive effect. Ang-(1-7) added to the perfusion solution (2 ng/ml) did not change the perfusion pressure or the contractile force but doubled the hypotensive effect of the lower doses of BK. The BK-potentiating Ang-(1-7) activity was blocked by pretreatment with indomethacin (5 mg/kg, ip) or L-NAME (30 mg/kg, ip). The Ang-(1-7) antagonist A-779 (50 ng/ml in Krebs-Ringer) completely blocked the effect of Ang-(1-7) on BK-induced vasodilation. These data suggest that the potentiation of the BK-induced vasodilation by Ang-(1-7) can be attributed to the release of nitric oxide and vasodilator prostaglandins through an Ang-(1-7) receptor-mediated mechanism.

Angiotensin peptides acting at rostral ventrolateral medulla contribute to hypertension of TGR(mREN2)27 rats

We have previously demonstrated that microinjections of the selective angiotensin-(1-7) [ANG-(1-7)] antagonist, A-779, into the rostral ventrolateral medulla (RVLM) produces a significant fall in mean arterial pressure (MAP) and heart rate (HR) in both anesthetized and conscious rats. In contrast, microinjection of angiotensin II (ANG II) AT(1) receptor antagonists did not change MAP in anesthetized rats and produced dose-dependent increases in MAP when microinjected into the RVLM of conscious rats. In the present study, we evaluated whether endogenous ANG-(1-7) and ANG II acting at the RVLM contribute to the hypertension of transgenic rats harboring the mouse renin Ren-2 gene, TGR(mREN2)27. Unilateral microinjection of A-779 (0.1 nmol) produced a significant fall in MAP (-25 +/- 5 mmHg) and HR (-57 +/- 20 beats/min) of awake TGR rats. The hypotensive effect was greater than that observed in Sprague-Dawley (SD) rats (-9 +/- 2 mmHg). Microinjection of the AT(1) antagonist CV-11974 (0.2 nmol) produced a fall in MAP in TGR rats (-14 +/- 4 mmHg), contrasting with the pressor effect observed in SD rats (33 +/- 9 mmHg). These results indicate that endogenous ANG-(1-7) exerts a significant pressor action in the RVLM, contributing to the hypertension of TGR(mREN2)27 transgenic rats. The role of ANG II at the RVLM seems to be dependent on its endogenous level in this area.

Opposing actions of angiotensins on angiogenesis

Using the murine sponge model of angiogenesis, associated to functional and morphological parameters we have demonstrated opposing actions of angiotensin II (Ang II) and angiotensin-(1-7;Ang-1-7) in modulating fibrovascular tissue growth. Angiogenesis in the implants was assessed at day 7 postimplantation by extracting the hemoglobin content, by determining the outflow rate of sodium fluorescein applied intraimplant and by histological analysis. Furthermore, the proliferative activity of control and angiotensin-treated implants was established using the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2(4 -sulfonyl)2H-tetrazolium)assay. The hemoglobin content in the control implants was 2.4 +/- 0.14 (microg/mg wet weight) versus 3.6 +/- 0.27(Ang II;100 ng) and 0.86 +/- 0.07 Ang-(1-7); 20 ng. Blood flow in the implants as determined by t1/2 values (time taken for the fluorescence to reach 50% of the peak in the systemic circulation) showed that Ang II stimulated angiogenesis, whereas Ang-(1-7) inhibited it. The proliferative activity of the sponge-induced fibrovascular tissue was enhanced by Ang II and diminished by Ang-(1-7). These results show the pro-versus anti-angiogenic effects of these angiotensin molecules, providing evidence for their opposing effects on vascular tissue growth and wound healing in vivo.

Effect of chronic angiotensin converting enzyme inhibition on angiotensin I and bradykinin metabolism in rats

We determined the effect of chronic administration of the angiotensin converting enzyme (ACE) inhibitor, enalapril, on the in vivo pulmonary inactivation of bradykinin (BK) and conversion of angiotensin I (Ang I). In addition we assessed whether chronic ACE inhibition influenced the activity of prolylendopeptidase (PEP), which metabolizes Ang I to generate angiotensin-(1-7) (Ang-[1-7]) and inactivates BK. Male Wistar rats were treated orally with enalapril (10 mg/kg once a day) for 7 to 15 days (n = 20) and 21 to 30 days (n = 11). Vehicle-treated rats (7 to 30 days, n = 11) were used as controls. Pulmonary inactivation of BK and conversion of Ang I were determined in conscious enalapril- or vehicle-treated rats before and after intravenous administration of the ACE inhibitor enalaprilat (MK-422, 10 mg/kg). Pulmonary inactivation of BK (%) was determined by comparing equipotent doses of BK injected by the intravenous and intraaortic routes, and Ang I conversion (%) by comparing the pressor effect of Ang I and Ang II injected intravenously. PEP-like activity in plasma and lung homogenates was determined fluorometrically using the synthetic substrate Suc-Gly-Pro-MCA. In control rats, pulmonary BK inactivation averaged 97.6% +/-0.54%. Acute ACE inhibition with MK-422 reduced BK inactivation to 42.0% +/- 2.7%. However, in rats treated chronically with enalapril, BK inactivation was increased as compared with acute ACE inhibition, averaging 58.8% +/- 3.7% at 7 to 15 days and 58.8% +/- 4.5% at 21 to 30 days of treatment. Intravenous administration of MK-422 to the enalapril-treated rats did not return the increased BK inactivation to the level observed during acute ACE inhibition. In contrast, Ang I conversion was significantly reduced from 46.7% +/- 6.5% to 0.9% +/-0.2% by MK-422, and this inhibition remained essentially unchanged during chronic treatment. PEP-like activity in plasma and lung homogenates of control rats was 4.4 +/- 0.3 nmol MCA/min/mL and 11.4 +/- 0.9 nmol MCA/min/mg protein, respectively. After chronic treatment with enalapril there was a progressive increase of PEP-like activity in both plasma and lung, which after 21 to 30 days of treatment averaged 10.7 +/- 1.7 nmol MCA/min/mL and 29.2 +/- 2.8 nmol MCA/min/mg protein, respectively. These data indicate that chronic ACE blockade induces alternative BK-inactivating mechanisms and increases Ang-(1-7)-generating mechanisms.

Haemorrhage increases the pressor effect of angiotensin-(1-7) but not of angiotensin II at the rat rostral ventrolateral medulla

OBJECTIVE

To evaluate the effects of angiotensins acting at the rostral ventrolateral medulla (RVLM) on the cardiovascular adjustments following haemorrhage.

DESIGN

Changes in mean arterial pressure (MAP) and heart rate (HR) produced by micro-injections of angiotensin II (Ang II) and angiotensin (Ang)-(1-7) and different angiotensin antagonists into the RVLM of anaesthetized rats submitted to haemorrhage, were determined.

METHODS

Experiments were performed in 79 urethane-anaesthetized male Wistar rats. Ang-(1-7) (2.5 and 25 pmol), Ang II (25 pmol), [Sar1,Thr8]-Ang II (non-selective angiotensin antagonist, 0.2 nmol), A-779 (Ang-(1-7) antagonist, 0.1 nmol), losartan (AT1 Ang II receptor antagonist, 0.2 nmol) or vehicle (200 nl) were bilaterally micro-injected into the RVLM under basal conditions or 30 min after blood withdrawal (0.6 ml/100 g bodyweight). In additional groups, [Sar1,Thr8]-Ang II, A-779, losartan or vehicle were micro-injected into the RVLM 10 min before bleeding to uncover a possible role of endogenous peptides during haemorrhage.

RESULTS

The pressor effect produced by Ang II micro-injection was not altered by haemorrhage. Conversely, haemorrhage significantly increased the magnitude and duration of the pressor effect of Ang-(1-7) at the RVLM. The fall in MAP induced by haemorrhage was similar after micro-injection of vehicle or A-779. However, micro-injection of [Sar1,Thr8]-Ang II significantly reduced the fall in MAP after haemorrhage. A similar finding was obtained with micro-injection of losartan. In addition, while RVLM micro-injection of [Sar1,Thr8]-Ang II or losartan 30 min after blood withdrawn produced MAP changes that were similar to that observed in control animals, micro-injection of A-779 did not significantly alter baseline MAP.

CONCLUSIONS

These results suggest that changes in the RVLM reactivity to Ang-(1-7) but not Ang II may contribute to the haemodynamic adjustments triggered by acute reductions in blood volume. The data obtained with [Sar1,Thr8]-Ang II and losartan suggest a primary inhibitory role for endogenous Ang II at the RVLM during haemorrhage.

Cardiovascular effects produced by nitric oxide-related drugs in the caudal ventrolateral medulla

The role of nitric oxide in the central control of blood pressure was evaluated by interfering with its local formation in the caudal region of the ventrolateral medulla (CVLM). Urethane anesthetized male Wistar rats were used. Microinjection of L-arginine (L-Arg, 25-100 nmol) produced a hypertensive effect without significant changes in heart rate (HR). Microinjection of N(G)-nitro-L-arginine methyl ester (L-NAME, 7.4 nmol) produced a significant hypotensive effect. Microinjection of L-Arg (50 nmol) combined with L-NAME (7.4 nmol) did not significantly change mean arterial pressure or HR. A similar finding was obtained with microinjection of L-Arg (50 nmol) 5 min after microinjection of methylene blue (5 nmol) into the CVLM. The pressor effect of L-Arg was also abolished by prior i.v. injection of a vasopressin V1 receptor antagonist, but not by prior i.v. injection of prazosin. These results suggest an inhibitory role for local NO in the CVLM and that nitrergic pathways at the CVLM participate in the central regulation of AVP release.

Synergistic effect of angiotensin-(1-7) on bradykinin arteriolar dilation in vivo

The interaction between angiotensin [Ang-(1-7)] and bradykinin (BK) was determined in the mesentery of anesthetized Wistar rats using intravital microscopy. Topical application of BK and Ang-(1-7) induced vasodilation that was abolished by the BK B2 receptor antagonist HOE-140 and the Ang-(1-7) antagonist A-779, respectively. BK (1 pmol)-induced vasodilation, but not SNP and ACh responses, was potentiated by Ang-(1-7) 10 pmol and 100 pmols. The effect of 100 pmol of Ang-(1-7) on BK-induced vasodilation was abolished by A-779, indomethacin, and L-nitroarginine methyl esther, whereas losartan was without effect. Enalaprilat treatment enhanced the BK- and Ang-(1-7)-induced vasodilation and the potentiating effect of Ang-(1-7) on BK vasodilation. The potentiation of BK-induced vasodilation by Ang-(1-7) is a receptor-mediated phenomenon dependent on cyclooxygenase-related products and NO release.

Potentiation of the hypotensive effect of bradykinin by angiotensin-(1-7)-related peptides

In this study, we evaluated the bradykinin potentiating activity and ACE inhibitory activity of several Ang-(1-7)-related peptides: Ang-(2-7), Ang-(3-7), Ang-(4-7), Ang-(1-6), Ang-(1-5) and the selective antagonist of Ang-(1-7): D-[Ala7]Ang-(1-7) (A-779). In vivo experiments were performed in freely moving Wistar rats. ACE activity was evaluated by a fluorometric assay in rat plasma using Hip-His-Leu as a substrate. Intravenous injections of Ang-(1-7) (2.2 nmol) transformed the effect of a single dose of bradykinin (1 nmol) into the effect produced by a double dose. A similar bradykinin potentiating activity was demonstrated for Ang-(2-7) and Ang-(3-7). On the other hand, Ang-(1-5), Ang-(1-6), Ang-(4-7) and A-779 did not change the hypotensive effect of bradykinin in doses ranging from 8 up to 25 nmols. The hypotensive effect of bradykinin was increased by intravenous infusion (0.3 ng/min) of Ang-(1-7) > Ang-(2-7) > Ang-(3-7). Conversely, Ang-(1-5), Ang-(1-6), Ang-(4-7) or A-779 did not change the hypotensive effect of bradykinin. ACE inhibition with Ang-(1-7) related peptides occurred in the order: Ang-(2-7) > or = Ang-(3-7) > Ang-(1-7) [>>] Ang-(1-5) > Ang-(4-7) > or = Ang-(1-6) > or = A-779. A-779 in concentrations up to 10(-5) M did not change the ACE inhibitory activity of Ang-(1-7). These results suggest that Ang-(1-7), Ang-(2-7) and Ang-(3-7) can modulate bradykinin actions in vivo. More important, our data pointed out that alternative mechanisms besides interaction with ACE are required to explain the bradykinin potentiating activity of Ang-(1-7).

Interaction of bradykinin and angiotensin-(1-7) in the central modulation of the baroreflex control of the heart rate

OBJECTIVE

Previous studies have shown that angiotensin-(1-7) potentiates the vascular actions of bradykinin. In the present study, we evaluated the interaction of bradykinin and angiotensin-(1-7) in the central modulation of baroreflex control of the heart rate.

MATERIALS AND METHODS

Blood pressure and reflex bradycardia, elicited by intravenous injection of phenylephrine, were evaluated in conscious male Wistar rats before and at the end of 1 h of an intracerebroventricular infusion of angiotensin-(1-7) at 0.5 or 1.0 microg/h combined with bradykinin at 2.5 microg/h; or angiotensin-(1-7) at 2.0 microg/h combined with bradykinin at 4.0 microg/h; or angiotensin-(1-7) alone at 2.0 or 4.0 microg/h; or bradykinin alone at 4.0 or 8.0 microg/h; or saline at 8 microl/h. In addition, baroreflex bradycardia was evaluated before and at the end of 1 and 2 h of intracerebroventricular infusion of angiotensin-(1-7) at 4 microg/h for 2 h; or saline at 8 microl/h in the first hour followed by HOE 140 at 90 ng/h in the second hour; or angiotensin-(1-7) at 4 microg/h in the first hour followed by angiotensin-(1-7) at 4 microg combined with HOE 140 at 90 ng/h in the second hour; or HOE 140 at 90 ng/h in the first hour followed by HOE 140 at 90th ng/h combined with angiotensin-(1-7) at 4 microg/h in the second hour; or saline at 8 microl/h for 2 h.

RESULTS

The intracerebroventricular infusion of angiotensin-(1-7) or bradykinin alone required a dose of 4.0 and 8.0 microg/h, respectively, to facilitate baroreflex control of the heart. However, a simultaneous infusion of these peptides at subeffective rates was able to produce a significant increase in baroreflex sensitivity. In addition, the facilitation of the baroreflex control of the heart rate induced by angiotensin-(1-7) at 4.0 microg/h was inhibited by HOE 140.

CONCLUSIONS

These results suggest that centrally, bradykinin and angiotensin-(1-7) can interact in order to modulate baroreflex control of the heart rate. In addition, our data indicate that the central modulatory effect of angiotensin-(1-7) on the baroreflex is mediated, at least in part, by the release of kinins.

Varicella-zoster virus glycoprotein gE: endocytosis and trafficking of the Fc receptor

Varicella-zoster virus (VZV) encodes a functional cell membrane Fc receptor called glycoprotein gE. VZV gE resembles other mammalian cell membrane receptors, such as the mammalian Fc receptor. In further analyses by transient transfection, the cellular trafficking of VZV gE was compared to other cell surface receptors. VZV gE was shown to undergo endocytosis from the cell membrane when visualized by laser scanning confocal microscopy. The endocytosis and trafficking pathway of VZV gE followed closely the pathway defined for the human transferrin receptor. Receptor-mediated endocytosis of VZV gE was dependent on a YAGL motif in its cytoplasmic tail. In addition, VZV gE underwent receptor-mediated endocytosis when it bound the Fc portion of immunoglobulin. Thus, this detailed study of VZV gE cellular trafficking has revealed potential roles for gE during viral infection.

Antigenic variation of varicella zoster virus Fc receptor gE: loss of a major B cell epitope in the ectodomain

Varicella zoster virus (VZV) is considered to possess a genetically stable genome; only one serotype is recognized around the world. The 125-kbp genome contains approximately 70 open reading frames. One that has received particular attention is open reading frame 68, which codes for glycoprotein gE, the predominant 623-residue viral envelope product that harbors both B and T cell epitopes. This report describes the initial characterization of a community-acquired VZV isolate that was a distinguishable second serotype (i.e., it had lost a major B cell epitope defined on the gE ectodomain by a murine monoclonal antibody called mAb 3B3). The mAb 3B3 epitope was found not only on the prototype sequenced Dumas strain from Holland and all previously tested North American isolates but also on the varicella vaccine Oka strain originally attenuated in Japan. Sequencing of the mutated gE ectodomain demonstrated that codon 150 exhibited a single base change that led to an amino acid change (aspartic acid to asparagine). Observation of the monolayers infected with the mutant VZV strain also led to the surprising discovery that the topography of egress was altered. Wild-type VZV emerges along distinctive viral highways, whereas the mutant strain virions were nearly uniformly distributed over the cell surface in a pattern more closely resembling egress of herpes simplex virus 1. The mutant VZV strain was designated VZV-MSP because it was isolated in Minnesota.