The evolution of early fibromuscular lesions hemodynamically induced in the dog renal artery. I. Light and transmission electron microscopy.
In view of the important roles of arterial intimal fibromuscular lesions as precursors of atherosclerotic plaque and occlusive lesions in arterial reconstructions, a model has been developed for the rapid hemodynamic induction of these lesions by anastomosis of the dog right renal artery to the inferior vena cava. Light and transmission electron microscopic observations were made on the arterial shunt after periods of rapid flow ranging form 10 minutes to 2 hours to identify initial factor(s) and evolutionary mechanisms in the etiology of the lesions. The sequence of events included aberrations in ruthenium red staining of the endothelial luminal membrane at 10 minutes, multilayered thickening of the subendothelial basement membrane (BM) at 15 minutes, and initial reorientation and migration of smooth muscle cells (SMC) into the intima along with the appearance of areas of degeneration of the internal elastic lamina (IEL) at 30 minutes. The endothelial cells were still intact in some areas overlying the SMC migration and IEL degeneration, but they were separating from the surface in other such areas. As subendothelium became exposed, some platelet adherence was noted. By 2 hours, the entire wall reaction was fully developed. Initial observations indicate that in the evolution of this hemodynamically induced lesion visible alteration in the endothelial cells is not prerequisite to degeneration of the underlying IEL and reorientation and migration of medial SMC. (+info)
Signal-, set- and movement-related activity in the human brain: an event-related fMRI study.
Electrophysiological studies on monkeys have been able to distinguish sensory and motor signals close in time by pseudorandomly delaying the cue that instructs the movement from the stimulus that triggers the movement. We have used a similar experimental design in functional magnetic resonance imaging (fMRI), scanning subjects while they performed a visuomotor conditional task with instructed delays. One of four shapes was presented briefly. Two shapes instructed the subjects to flex the index finger; the other two shapes coded the flexion of the middle finger. The subjects were told to perform the movement after a tone. We have exploited a novel use of event-related fMRI. By systematically varying the interval between the visual and acoustic stimuli, it has been possible to estimate the significance of the evoked haemodynamic response (EHR) to each of the stimuli, despite their temporal proximity in relation to the time constant of the EHR. Furthermore, by varying the phase between events and image acquisition, we have been able to achieve high temporal resolution while scanning the whole brain. We dissociated sensory and motor components of the sensorimotor transformations elicited by the task, and assessed sustained activity during the instructed delays. In calcarine and occipitotemporal cortex, the responses were exclusively associated with the visual instruction cues. In temporal auditory cortex and in primary motor cortex, they were exclusively associated with the auditory trigger stimulus. In ventral prefrontal cortex there were movement-related responses preceded by preparatory activity and by signal-related activity. Finally, responses associated with the instruction cue and with sustained activity during the delay period were observed in the dorsal premotor cortex and in the dorsal posterior parietal cortex. Where the association between a visual cue and the appropriate movement is arbitrary, the underlying visuomotor transformations are not achieved exclusively through frontoparietal interactions. Rather, these processes seem to rely on the ventral visual stream, the ventral prefrontal cortex and the anterior part of the dorsal premotor cortex. (+info)
Protective effect of bactericidal/permeability-increasing protein (rBPI21) in baboon sepsis is related to its antibacterial, not antiendotoxin, properties.
OBJECTIVE AND SUMMARY BACKGROUND DATA: The recombinant fragment of bactericidal/permeability-increasing protein, rBPI21, has potent bactericidal activity against gram-negative bacteria as well as antiendotoxin (lipopolysaccharide [LPS]) action. On the basis of these activities, the authors sought to discover whether rBPI21 would be protective in baboons with live Escherichia coli-induced sepsis and whether the potential protective effects of rBPI21 (together with antibiotics) would be more closely related to its antibacterial or LPS-neutralizing effects. METHODS: In a prospective, randomized, placebo-controlled subchronic laboratory study, the efficacy of rBPI21 or placebo was studied over 72 hours in chronically instrumented male baboons infused with live E. coli under antibiotic therapy. RESULTS: Intravenous rBPI21 attenuated sepsis-related organ failure and increased survival significantly. Bacteremia was significantly reduced in the rBPI21 group at 2 hours after the start of the E. coli infusion, whereas circulating LPS was less affected. The in vivo formation of tumor necrosis factor was significantly suppressed by the rBPI21 treatment regimen. Microcirculation and organ function were improved. CONCLUSIONS: In baboon live E. coli sepsis, the salutary effect of rBPI21 results from a more prevalent antibacterial than antiendotoxin activity. (+info)
NaCl-induced renal vasoconstriction in salt-sensitive African Americans: antipressor and hemodynamic effects of potassium bicarbonate.
In 16 African Americans (blacks, 14 men, 2 women) with average admission mean arterial pressure (MAP, mm Hg) 99.9+/-3.5 (mean+/-SEM), we investigated whether NaCl-induced renal vasoconstriction attends salt sensitivity and, if so, whether supplemental KHCO3 ameliorates both conditions. Throughout a 3-week period under controlled metabolic conditions, all subjects ate diets containing 15 mmol NaCl and 30 mmol potassium (K+) (per 70 kg body wt [BW] per day). Throughout weeks 2 and 3, NaCl was loaded to 250 mmol/d; throughout week 3, dietary K+ was supplemented to 170 mmol/d (KHCO3). On the last day of each study week, we measured renal blood flow (RBF) and glomerular filtration rate (GFR) using renal clearances of PAH and inulin. Ten subjects were salt sensitive (SS) (DeltaMAP >+5%) and 6 salt resistant (SR). In NaCl-loaded SS but not SR subjects, RBF (mL/min/1.73 m2) decreased from 920+/-75 to 828+/-46 (P<0.05); filtration fraction (FF, %) increased from 19. 4+/- to 21.4 (P<0.001); and renal vascular resistance (RVR) (10(3)xmm Hg/[mL/min]) increased from 101+/-8 to 131+/-10 (P<0.001). In all subjects combined, DeltaMAP varied inversely with DeltaRBF (r =-0.57, P=0.02) and directly with DeltaRVR (r = 0.65, P=0.006) and DeltaFF (r = 0.59, P=0.03), but not with MAP before NaCl loading. When supplemental KHCO3 abolished the pressor effect of NaCl in SS subjects, RBF was unaffected but GFR and FF decreased. The results show that in marginally K+-deficient blacks (1) NaCl-induced renal vasoconstrictive dysfunction attends salt sensitivity; (2) the dysfunction varies in extent directly with the NaCl-induced increase in blood pressure (BP); and (3) is complexly affected by supplemented KHCO3, GFR and FF decreasing but RBF not changing. In blacks, NaCl-induced renal vasoconstriction may be a pathogenetic event in salt sensitivity. (+info)
Low calorie diet enhances renal, hemodynamic, and humoral effects of exogenous atrial natriuretic peptide in obese hypertensives.
The expression of the natriuretic peptide clearance receptor is abundant in human and rat adipose tissue, where it is specifically inhibited by fasting. In obese hypertensives, plasma atrial natriuretic peptide (ANP) levels were found to be lower than in obese normotensives. Therefore, the increased adipose mass might influence ANP levels and/or its biological activity. The aim of the present study was to evaluate whether the humoral, hemodynamic, and renal effects of exogenous ANP in obese hypertensives might be enhanced by a very low calorie diet. Eight obese hypertensives received a bolus injection of ANP (0.6 mg/kg) after 2 weeks of a normal calorie/normal sodium diet, and blood pressure (BP), heart rate, ANP, cGMP, plasma renin activity, and aldosterone were evaluated for 2 hours before and after the injection. Diuresis and natriuresis were measured every 30 minutes. The patients then started a low calorie/normal sodium diet (510 kcal/150 mmol/d) for 4 days, and then the ANP injection protocol was repeated. The low calorie diet induced a slight weight loss (from 90.6+/-1.1 to 87. 7+/-1.2 kg; P<0.01), which was accompanied by increase of cGMP excretion (from 146.0+/-10.1 to 154.5+/-9.5 nmol/24 h; P<0.05) together with a reduction of BP (P<0.01 versus basal levels). ANP injection after diet was followed by an increase of ANP levels similar to that observed before diet, but plasma cGMP, diuresis, and natriuresis increased significantly only after diet. Similarly, the decrease of BP after ANP administration was significantly higher after diet (change in mean arterial pressure, -6.4+/-0.7 versus -4. 0+/-0.6 mm Hg; P<0.05) as well as that of aldosterone (P<0.01). These data show that a low calorie diet enhances the humoral, renal, and hemodynamic effects of ANP in obese hypertensives and confirm the importance of caloric intake in modulating the biological activity of ANP, suggesting that the natriuretic peptide system can play a role in the acute changes of natriuresis and diuresis associated with caloric restriction. (+info)
Sympathetic nerve alterations assessed with 123I-MIBG in the failing human heart.
Norepinephrine (NE) reuptake function is impaired in heart failure and this may participate in myocyte hyperstimulation by the neurotransmitter. This alteration can be assessed by 123I-metaiodobenzylguanidine (MIBG) scintigraphy. METHODS: To determine whether the impairment of neuronal NE reuptake was reversible after metoprolol therapy, we studied 18 patients (43+/-7 y) with idiopathic dilated cardiomyopathy who were stabilized at least for 3 mo with captopril and diuretics. Patients underwent, before and after 6 mo of therapy with metoprolol, measurements of radionuclide left ventricular ejection fraction (LVEF), maximal oxygen consumption and plasma NE concentration. The cardiac adrenergic innervation function was scintigraphically assessed with MIBG uptake and release measurements on the planar images obtained 20 min and 4 h after tracer injection. To evaluate whether metoprolol had a direct interaction with cardiac MIBG uptake and release, six normal subjects were studied before and after a 1-mo metoprolol intake. RESULTS: In controls, neither cardiac MIBG uptake and release nor circulating NE concentration changed after the 1-mo metoprolol intake. Conversely, after a 6-mo therapy with metoprolol, patients showed increased cardiac MIBG uptake (129%+/-10% versus 138%+/-17%; P = 0.009), unchanged cardiac MIBG release and decreased plasma NE concentration (0.930+/-412 versus 0.721+/-0.370 ng/mL; P = 0.02). In parallel, patients showed improved New York Heart Association class (2.44+/-0.51 versus 2.05+/-0.23; P = 0.004) and increased LVEF (20%+/-8% versus 27%+/-8%; P = 0.0005), whereas maximal oxygen uptake remained unchanged. CONCLUSION: Thus, a parallel improvement of myocardial NE reuptake and of hemodynamics was observed after a 6-mo metoprolol therapy, suggesting that such agents may be beneficial in heart failure by directly protecting the myocardium against excessive NE stimulation. (+info)
Enteroviral RNA replication in the myocardium of patients with left ventricular dysfunction and clinically suspected myocarditis.
BACKGROUND: Previous studies dealing with the detection of enteroviral RNA in human endomyocardial biopsies have not differentiated between latent persistence of the enteroviral genome and active viral replication. Enteroviruses that are considered important factors for the development of myocarditis have a single-strand RNA genome of positive polarity that is transcribed by a virus-encoded RNA polymerase into a minus-strand mRNA during active viral replication. The synthesis of multiple copies of minus-strand enteroviral RNA therefore occurs only at sites of active viral replication but not in tissues with mere persistence of the viral genome. METHODS AND RESULTS: We investigated enteroviral RNA replication versus enteroviral RNA persistence in endomyocardial biopsies of 45 patients with left ventricular dysfunction and clinically suspected myocarditis. Using reverse-transcriptase polymerase chain reaction in conjunction with Southern blot hybridization, we established a highly sensitive assay to specifically detect plus-strand versus minus-strand enteroviral RNA in the biopsies. Plus-strand enteroviral RNA was detected in endomyocardial biopsies of 18 (40%) of 45 patients, whereas minus-strand RNA as an indication of active enteroviral RNA replication was detected in only 10 (56%) of these 18 plus-strand-positive patients. Enteroviral RNA was not found in biopsies of the control group (n=26). CONCLUSIONS: These data demonstrate that a significant fraction of patients with left ventricular dysfunction and clinically suspected myocarditis had active enteroviral RNA replication in their myocardium (22%). Differentiation between patients with active viral replication and latent viral persistence should be particularly important in future studies evaluating different therapeutic strategies. In addition, molecular genetic detection of enteroviral genome and differentiation between replicating versus persistent viruses is possible in a single endomyocardial biopsy. (+info)
Suppression of atherosclerotic development in Watanabe heritable hyperlipidemic rabbits treated with an oral antiallergic drug, tranilast.
BACKGROUND: Inflammatory and immunological responses of vascular cells have been shown to play a significant role in the progression of atheromatous formation. Tranilast [N-(3,4-dimethoxycinnamoyl) anthranillic acid] inhibits release of cytokines and chemical mediators from various cells, including macrophages, leading to suppression of inflammatory and immunological responses. This study tested whether tranilast may suppress atheromatous formation in Watanabe heritable hyperlipidemic (WHHL) rabbits. METHODS AND RESULTS: WHHL rabbits (2 months old) were given either 300 mg x kg-1 x d-1 of tranilast (Tranilast, n=12) or vehicle (Control, n=13) PO for 6 months. Tranilast treatment was found to suppress the aortic area covered with plaque. Immunohistochemical analysis showed that there was no difference in the percentage of the RAM11-positive macrophage area and the frequency of CD5-positive cells (T cells) in intimal plaques between Tranilast and Control. Major histocompatibility complex (MHC) class II expression in macrophages and interleukin-2 (IL-2) receptor expression in T cells, as markers of the immunological activation in these cells, was suppressed in atheromatous plaque by tranilast treatment. Flow cytometry analysis of isolated human and rabbit peripheral blood mononuclear cells showed that an increase in expression both of MHC class II antigen on monocytes by incubation with interferon-gamma and of IL-2 receptor on T cells by IL-2 was suppressed by the combined incubation with tranilast. CONCLUSIONS: The results indicate that tranilast suppresses atherosclerotic development partly through direct inhibition of immunological activation of monocytes/macrophages and T cells in the atheromatous plaque. (+info)