Inclusive multisensory science and immunology books for blind, low-vision and diverse-needs audiences

This paper presents interdisciplinary research exploring the development of inclusive multisensory science books, communicating immunology data for blind, low-vision and diverse-needs audiences. The research adopted an inductive theory-building approach, practice-based art methods and music and design methods, leveraging the lived experience of a legally blind artist. The research also involved designers and scientists in a cocreation process, producing books that incorporate tactile artworks, Braille-inspired protein models, image sonification and interaction. Two multisensory book titles, "The Heroes Within You: A Multisensory Exploration of Infection and Immunity" and "My Goodness: A Multisensory Exploration of Nutrition and Immunity", were developed for the Monash Sensory Science 2023 Exhibition Day. The books offer an innovative way to make science and art more accessible and engaging, addressing the limitations of traditional museum methods. Feedback from audiences has been positive, emphasizing the fascination, sensory engagement and ease of understanding. This paper highlights the potential for an interdisciplinary and inclusive approach to science and art, demonstrating the value of multisensory books as tools for science communication. The findings highlight the positive reception of this novel approach and suggest its potential for broader applications, promoting inclusivity and accessibility.

Art, science and inclusion: multisensory Sciart of immunology for blind, low-vision and diverse-needs audiences

Art is a powerful tool for conveying scientific discovery. Despite the perceived gap between art and science, as highlighted by CP Snow and others, examples of art communicating science can be found in the ancient world, the Renaissance and contemporary data visualization, demonstrating an enduring and historic connection. However, much of science relies on visual elements, excluding those with blindness, low vision and diverse needs, resulting in their low representation in STEM discourse. This paper introduces a novel science and art collaboration in the form of an exhibition program exploring the concepts of Immunology and Biomedicine to blind and vision-impaired audiences, capitalizing on the lived experience of a legally blind artist. Employing multisensory design, art and co-creation methodologies, it transcends traditional vision-based science communication, showcasing the potential for multisensory art to bridge the gap at the intersection of science and inclusion.

Access all areas: multisensory science exhibitions tailored toward blind, low-vision and diverse-needs communities

Monash Sensory Science is a scientific outreach initiative specifically tailored to members of the community who are blind, have low vision and have diverse needs. The purpose of this initiative is to showcase Australian science and encourage greater participation in science from these often-overlooked communities. This article presents our experience in establishing Monash Sensory Science at Monash University and inspiring other institutions to launch similar outreach events.

Occurrence of Soluble Very High Molecular Weight Fibrinogen Complexes in Hypercoagulable States. An in vitro and in vivo Study on their Features

The gel-chromatography of the beta-alanine precipitate of human plasma and of purified fibrinogen shows the presence of different classes of fibrinogen complexes. A first class of complexes is detectable in correspondence with the ascending branch of the fibrinogen peak (“shoulder” complexes or high molecular weight fibrinogen complexes, HMWFC). A second class of complexes at very high molecular weight is eluted at the void volume (peak 1 complexes or VHMWFC). Treatment of plasma or fibrinogen in vitro with thrombin induces the formation of both classes of complexes. Also thrombin infusion in rabbits induces an increase of both VHMWFC and HMWFC; pretreatment with heparin prevents these changes. In the detection of VHMWF 4% agarose and beta-alanine precipitation seem to be necessary for a good resolution of the chromatographic profile. VHMWFC are devoid of albumin, transferrin and immunoglobulins on radial immunodiffusion and their elution volume suggests a molecular weight over 1 million. They show a procoagulant activity; namely they accelerate the fibrinogen polymerization and increase the resistance of normal plasma to heparin. They also induce the formation of platelet aggregates, reversible in EDTA, when incubated without stirring with control PRP, but in Born apparatus in presence of ADP they show a slight antiaggregating activity. In normal healthy young volunteers (control group A) the average values were respectively 7.81 ± 3.53 mg% for VHMWFC and 12.19 ± 4.74 mg% for HMWFC. Both VHMWFC and HMWFC are increased in patients with hypercoagulable states (patients with history of myocardial infarction, MIP, with chronic cerebrovascular disorders, CVP, with acute thrombophlebitis and with subacute intravascular coagulation, cancer patients). The increase of VHMWFC and HMWFC is however different in the various groups of patients. An increase predominantly of VHMWFC (sometimes with normal HMWFC) is detectable in MIP and CVP, whereas in subjects with acute thrombophlebitis and with cancer a predominant increase of HMWFC associated with increased levels of FDP is detectable. The detection of VHMWFC represents a useful tool for the evaluation of hypercoagulable state, and their occurrence can cooperate to enhance hypercoagulability as VHMWFC possess procoagulant activity.

Changes of Platelet Function and Blood Clotting in Diabetes Mellitus

We investigated some aspects of blood clotting and of platelet functions in 48 diabetics (12 affected by preclinical diabetes, 15 by clinical diabetes, 21 with complications of diabetes, peripheral vascular disease, ischaemic heart disease or diabetic nephropathy with or without hypertension) in 35 age matched controls and in 7 prediabetics.

Blood clotting has been investigated by gel-chromatography of fibrin soluble complexes, by factor VIIICOAG two stage assay, by factor VIIIAGN electroimmunodiffusion assay and by factor VIIIvWF assay. Platelet functions have been investigated by the determination of circulating platelet aggregates associated with megathrombocytes count, by the malondial- dehyde formation after thrombin and after arachidonic acid. In order to clarify some mechanisms responsible for platelet aggregating plasmatic activity (PAPA) has been investigated by plasmaplatelet cross-matches.

Our results indicate early changes of platelet functions in diabetics, already demonstrable in preclinical diabetes. Platelets are hyperaggregable and produce increased amounts of malondialdehyde after stimulation by thrombin and arachidonic acid, thus suggesting an increased activity of the intraplatelet endoperoxide-thromboxane forming metabolic pathway. An increased concentration of fibrin soluble complexes can be shown in clinical and complicated diabetes whereas in preclinical diabetes the fibrogen complexes concentration is within the normal range.

Factor VIIIvWF results significantly increased in all groups of diabetics, and even in the subjects with prediabetes. Factor VHICoag and Factor VIIIAGN, besides factor VIIIvWF, were significantly increased in clinical and in complicated diabetes. The increased concentration of factor VIIICOAG and of soluble fibrinogen complexes suggest the existence of a hypercoagulable condition in patients with clinical and above all with complicated diabetes.

In these patients a platelet aggregating plasmatic activity can be frequently found. The indication is that platelet hyperaggregation in diabetes is due to various mechanisms. In preclinical diabetes and in some patients with clinical diabetes platelet hyperaggregability is mainly due to a primary platelet hypersensitivity whereas in complicated diabetes, specially when hypercoagulability occurs, platelet hyperaggregation is due to a plasmatic factor related to blood clotting activation.

Complications related to fracture treatment in HIV patients: a case report

We present the case report of a 40-year-old woman who was HIV-positive in Highly Active Anti-Retroviral Therapy (HAART) and affected by femural pertrochanteric fracture, which was treated by endomedullary nailing. Two years after the surgical operation, the woman developed an aseptic symptomatic osteolysis around the implant. Hardware removal was resolutive. Aseptic and septic hardware mobilization, hardware removal, and implant decision in HIV patients with pertrochanteric fractures is discussed. The authors suggest close follow-up and prompt hardware removal, as soon as X-rays demonstrate healing signs, in HIV patients with fracture fixation, if general condition allows.

Quantitative versus qualitative modeling: a complementary approach in ecosystem study

Natural disturbance or human perturbation act upon ecosystems by changing some dynamical parameters of one or more species. Foreseeing these modifications is necessary before embarking on an intervention: predictions may help to assess management options and define hypothesis for interventions. Models become valuable tools for studying and making predictions only when they capture types of interactions and their magnitude. Quantitative models are more precise and specific about a system, but require a large effort in model construction. Because of this very often ecological systems remain only partially specified and one possible approach to their description and analysis comes from qualitative modelling. Qualitative models yield predictions as directions of change in species abundance but in complex systems these predictions are often ambiguous, being the result of opposite actions exerted on the same species by way of multiple pathways of interactions. Again, to avoid such ambiguities one needs to know the intensity of all links in the system. One way to make link magnitude explicit in a way that can be used in qualitative analysis is described in this paper and takes advantage of another type of ecosystem representation: ecological flow networks. These flow diagrams contain the structure, the relative position and the connections between the components of a system, and the quantity of matter flowing along every connection. In this paper it is shown how these ecological flow networks can be used to produce a quantitative model similar to the qualitative counterpart. Analyzed through the apparatus of loop analysis this quantitative model yields predictions that are by no means ambiguous, solving in an elegant way the basic problem of qualitative analysis. The approach adopted in this work is still preliminary and we must be careful in its application.

Is Hyperhomocyst(e)inemia A Humoral Predictor of Coronary Heart Disease?

Elevated plasma homocyst(e)ine levels have prothrombotic and proatherosclerotic effects. Data from prospective studies indicated that plasma homocyst(e)ine acts as a modest independent predictor of coronary heart disease. At present, no conclusive data are available on the possible interaction between hyperhomocyst(e)inemia and hypertension and the occurrence of cardiovascular events. Recent longitudinal studies in high risk patients indicated that hyperhomocyst(e)inemia is strongly associated with recurrent cardiovascular events. However, this finding is not in line with the few available data from prospective studies, which failed to observe a protective role of homocyst(e)ine-lowering therapy in secondary prevention of cardiovascular events. Future results from ongoing larger trials are expected to provide more definitive answers concerning the need to support the routine use of folic acid in patients with CHD. Since the definitive impact of mild hyperhomocyst(e)inemia on coronary heart disease is still to be established, widespread determination of homocyst(e)ine levels is not needed in a general population at the present time. In contrast, knowledge of homocyst(e)inemia may be important for specific groups of individuals, such as high risk patients, and for those patients in whom traditional risk factors do not appear to account for an increased incidence of cardiovascular events.

Mechanisms responsible for endothelial dysfunction induced by fasting hyperhomocystinemia in normotensive subjects and patients with essential hypertension

OBJECTIVES

We sought to evaluate whether fasting hyperhomocystinemia reduces endothelial function by oxidative stress in normotensive subjects and hypertensive patients.

BACKGROUND

Subjects with hyperhomocystinemia have endothelial dysfunction.

METHODS

In 23 normotensive subjects and 28 hypertensive patients, classified into normohomocystinemic and hyperhomocystinemic groups according to homocysteine plasma levels (< 8.7 and >14.6 micromol/l, respectively), we studied forearm blood flow changes (strain-gauge plethysmography) induced by intrabrachial administration of acetylcholine (0.15 to 15 microg/100 ml tissue per min) or sodium nitroprusside (1 to 4 microg/100 ml per min), an endothelium-dependent and -independent vasodilator, respectively. Acetylcholine was repeated with N(G)-monomethyl-L-arginine (L-NMMA; 100 microg/100 ml per min), vitamin C (8 mg/100 ml per min) and L-NMMA plus vitamin C.

RESULTS

Normotensive hyperhomocystinemic patients showed a blunted response to acetylcholine and a lower inhibiting effect of L-NMMA on acetylcholine, as compared with normohomocystinemic patients. Although vitamin C was ineffective in normohomocystinemic subjects, it increased the response to acetylcholine and restored the inhibiting effect of L-NMMA on acetylcholine in hyperhomocystinemic patients. Hypertensive hyperhomocystinemic patients showed a reduced response to acetylcholine, as compared with normohomocystinemic subjects. In both subgroups, L-NMMA failed to blunt the response to acetylcholine. The potentiating effect of vitamin C on acetylcholine was greater in hyperhomocystinemic patients than in normohomocystinemic subjects, although it restored the inhibitory effect of L-NMMA on acetylcholine-induced vasodilation to the same extent in both groups. Hyperhomocystinemia did not change the response to sodium nitroprusside.

CONCLUSIONS

In normotensive subjects and hypertensive patients, hyperhomocystinemia impairs endothelium-dependent vasodilation. It could be related to oxidant activity.

Restoration of nitric oxide availability after calcium antagonist treatment in essential hypertension

Essential hypertension is associated with impaired endothelium-dependent vasodilation caused by oxygen free radical-induced nitric oxide (NO) breakdown. Because calcium antagonists can improve endothelial function in patients with essential hypertension, in this study we tested the hypothesis that this beneficial effect could be related to restoration of NO availability by antioxidant properties. In 15 healthy subjects and 15 hypertensive patients, we studied forearm blood flow (strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (ACh; 0.15, 0.45, 1.5, 4.5, and 15 microg/100 mL per minute), an endothelium-dependent vasodilator in basal conditions, during infusion of N:(G)-monomethyl-L-arginine (L-NMMA, 100 microg/100 mL forearm tissue per minute), an NO-synthase inhibitor, vitamin C (8 mg/100 mL forearm tissue per minute), and finally, simultaneous infusion of L-NMMA and vitamin C. The response to sodium nitroprusside (SNP; 1, 2, and 4 microg/100 mL forearm tissue per minute) was also evaluated. In control subjects, vasodilation to ACh was inhibited by L-NMMA and not changed by vitamin C. In hypertensive patients, vasodilation to ACh was blunted as compared with control subjects and resistant to L-NMMA. Vitamin C, which decreased plasma isoprostanes and increased plasma antioxidant capacity, increased the response to ACh and restored the inhibiting effect of L-NMMA. In hypertensive patients, the study was repeated after 3-month treatment with nifedipine gastrointestinal therapeutic system (30 to 60 mg/daily). Nifedipine treatment decreased circulating plasma lipoperoxides and isoprostanes and increased plasma antioxidant capacity. Moreover, nifedipine increased the vasodilation to ACh but not to SNP and restored the inhibiting effect of L-NMMA on ACh-induced vasodilation, whereas vitamin C no longer exerted its facilitating activity. These results indicate that nifedipine increases endothelium-dependent vasodilation by restoring NO availability, an effect probably determined by antioxidant activity.

Exclusion of the ACE D/I gene polymorphism as a determinant of endothelial dysfunction

A deletion/insertion (D/I) polymorphism within the ACE gene may increase the risk of cardiovascular events through still unknown mechanisms. The latter may involve increased angiotensin II-induced NO breakdown and/or reduced agonist-mediated NO release. We therefore investigated whether the D allele of the ACE gene affects endothelium-dependent vasodilatation in mild-to-moderate primary hypertensive patients and healthy normotensive subjects. We compared in a cross-sectional study the forearm blood flow response of the 3 D/I genotypes with 5 incrementally increasing doses of the endothelium-dependent vasodilator acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 microg. 100 mL(-1). min(-1)) in 142 subjects: 103 mild-to-moderate uncomplicated primary hypertensives (49.3+/-9.1 years old, 152+/-11/99+/-5 mm Hg) and 39 normotensives (44.6+/-15.3 years old, 122+/-12/78+/-6 mm Hg). We also assessed the endothelium-independent vasodilatation in the forearm, as blood flow response to 3 incrementally increasing doses of sodium nitroprusside (1, 2, and 4 microg. 100 mL(-1). min(-1)). The overall genotype distribution was II, n=10; ID, n=70; and DD, n=62. It did not differ significantly between primary hypertensives and normotensives. A significant blunting of endothelium-dependent vasodilatation in primary hypertensive patients compared with normotensive subjects (P:<0.001) was found. No effect of the DI genotype on endothelium-dependent and -independent vasodilatation was detected. Thus, these results obtained in a relatively large population do not support the contention that the D allele is associated with a blunting of either stimulated endothelial NO or donated NO responses in both mild-to-moderate primary hypertensive patients and normotensive subjects.

Relationship between the circulating and vascular renin-angiotensin system and the vasodilating effect of captopril in human hypertension

A vascular renin-angiotensin system (RAS) is present in the forearm vasculature of essential hypertensive patients and is closely related to the circulating renin profile. To test whether the haemodynamic effect of acute intrabrachial administration of captopril is related to the circulating and/or vascular RAS, 31 hypertensive patients were selected and divided into four groups according to their different circulating RAS profile (n = 7 hypertensive patients with primary aldosteronism and suppressed plasma renin activity; n = 7 low renin essential hypertensive patients; n = 8 normal renin essential hypertensive patients; n = 9 high renin renovascular hypertensive patients). The forearm net balance of active renin, plasma renin activity and angiotensin II, obtained by intrabrachial infusion of the beta-adrenergic receptor agonist isoproterenol (0.03, 0.1, 0.3 microg/100 ml/min) and calculated as the product of the venous-arterial plasma concentration gradient and forearm blood flow (FBF), was closely related to the circulating RAS. Captopril (0.25, 2.5, 25 microg/100 ml/min per 20 min each dose) unchanged basal FBF in the primary aldosteronism and low renin groups (FBF increase: from 3.9 +/- 0.4 to a maximum of 4.1 +/- 0.5 and from 3.8 +/- 0.3 to a maximum of 4.3 +/- 0.5 ml/100 ml/min, respectively), whereas it caused slight vasodilation in the normal renin group (from 3.9 +/- 0.3 to a maximum of 5.3 +/- 0.7 ml/100 ml/min), and pronounced vasodilation in the high renin group (from 4.0 +/- 0.4 to a maximum of 6.4 +/- 0.5 ml/100 ml/min). Captopril-induced vasodilation showed a significant direct correlation with the circulating and vascular RAS. The present data, while confirming the existence of a vascular RAS in the forearm of hypertensive patients indicate that the acute vasodilating effect of intrabrachial captopril is linked to a stimulated RAS, either circulating or vascular, supporting the evidence that, in acute conditions, ACE inhibitors exert their vasodilating effect through the RAS blockade.

Adenosine causes the release of active renin and angiotensin II in the coronary circulation of patients with essential hypertension

OBJECTIVES

The aim of the study was to evaluate whether adenosine infusion can induce production of active renin and angiotensin II in human coronary circulation.

BACKGROUND

Adenosine can activate angiotensin production in the forearm vessels of essential hypertensive patients.

METHODS

In six normotensive subjects and 12 essential hypertensive patients adenosine was infused into the left anterior descending coronary artery (1, 10, 100 and 1,000 microg/min x 5 min each) while active renin (radioimmunometric assay) and angiotensin II (radioimmunoassay after high performance liquid chromatography purification) were measured in venous (great cardiac vein) and coronary arterial blood samples. In five out of 12 hypertensive patients adenosine infusion and plasma samples were repeated during intracoronary angiotensin-converting enzyme inhibitor benazeprilat (25 microg/min) administration. Finally, in adjunctive hypertensive patients, the same procedure was applied during intracoronary sodium nitroprusside (n = 4) or acetylcholine (n = 4).

RESULTS

In hypertensive patients, but not in control subjects, despite a similar increment in coronary blood flow, a significant (p < 0.05) transient increase of venous active renin (from 10.7 +/- 1.4 [95% confidence interval 9.4 to 11.8] to a maximum of 13.8 +/- 2.1 [12.2 to 15.5] with a consequent drop to 10.9 +/- 1.8 [9.7 to 12.1] pg/ml), and angiotensin II (from 14.6 +/- 2.0 [12.7 to 16.5] to a maximum of 20.4 +/- 2.7 [18.7 to 22.2] with a consequent drop to 16.3 +/- 1.8 [13.9 to 18.7] pg/ml) was observed under adenosine infusion, whereas arterial values did not change. Calculated venous-arterial active renin and angiotensin II release showed a strong correlation (r = 0.78 and r = 0.71, respectively; p < 0.001) with circulating active renin. This adenosine-induced venous angiotensin II increase was significantly blunted by benazeprilat. Finally, both sodium nitroprusside and acetylcholine did not affect arterial and venous values of active renin and angiotensin II.

CONCLUSIONS

These data indicate that exogenous adenosine stimulates the release of active renin and angiotensin II in the coronary arteries of essential hypertensive patients, and suggest that this phenomenon is probably due to renin release from tissue stores of renally derived renin.

Humoral and haemodynamic effects of idrapril calcium, the prototype of a new class of ACE-inhibitors, in essential hypertensive patients

Idrapril is the prototype of a new class of ACE inhibitors, characterised by the presence of a hydroxdmic group. Six untreated in-patients with essential hypertension were given single oral doses of the calcium salt of idrapril, idrapril calcium (200 mg) and placebo according to a double blind, randomised experimental design. Supine and upright blood pressure, heart rate, plasma idrapril serum UCE, active renin and angiotensin II were measured at timed intervals for 24 hours after dosing. Plasma idrapril reached a peak after 2 hours (3.01 microgm x ml(-1)), and by 12 hours the compound had almost disappeared (67 ng x ml(-1)). Derived t1/2 was 1.4-2.2 h. ACE activity was suppressed [from 77.9 to 3.3 after 2 hours and 11.8 after 12 hours nmol(-1) x min(-1) x ml] and angiotensin II production inhibited [from 8.8 to 3.1 (after 1 hour) and 7.5 (after 24 hours) pg x ml(-1)]. Compared to placebo, idrapril calcium significantly lowered both supine blood pressure starting at 4 hours (idrapril calcium 140/93 mmHg; placebo 157/101 mmHg; placebo 147/100 mmHg), and upright blood pressure starting at 3 hours (idrapril calcium 135/95 mmHg; placebo 147/100 mmHg) up to 24 hours (idrapril calcium 132/92 mmHg; placebo 145/100 mmHg). Idrapril calcium appears to be an effective ACE inhibitor in essential hypertension, with a hypotensive action for up to 24 h.

Angiotensin II and sympathetic activity in sodium-restricted essential hypertension

Angiotensin II (Ang II) potentiates sympathetic neurotransmission by presynaptic facilitation of norepinephrine release. We investigated whether endogenous Ang II modulates peripheral sympathetic activity in sodium-depleted essential hypertensive patients. We evaluated the effect of intrabrachial infusion of saralasin, an Ang II antagonist (5 micrograms/100 mL forearm tissue per minute), and benazeprilat, an angiotensin-converting enzyme inhibitor (2 micrograms/100 mL forearm tissue per minute), on forearm vasoconstriction (measured by strain-gauge venous plethysmography) induced by the application of lower body negative pressure (-10 mm Hg for 5 minutes). Both saralasin and benazeprilat (n = 6 for each group) blunted the vasoconstrictor action of lower body negative pressure, suggesting that circulating Ang II modulates peripheral sympathetic activity. In addition, since beta-adrenoceptor stimulation can activate the production of vascular Ang II, the effect of saralasin and benazeprilat on lower body negative pressure application was evaluated in the presence of isoproterenol (0.09 microgram/100 mL forearm tissue per minute) and propranolol (10 micrograms/100 mL forearm tissue per minute). In two other groups of hypertensive patients, isoproterenol infusion increased the release of Ang II in the forearm vasculature (arteriovenous values measured by radioimmunoassay). Furthermore, isoproterenol potentiated lower body negative pressure-induced vasoconstriction. This facilitating effect was abolished by either saralasin or benazeprilat (n = 6 for each group). In contrast, in two further groups of patients (n = 6 for each group), in the presence of the beta-blocker propranolol saralasin and benazeprilat did not alter the vasoconstrictor action of the endogenous sympathetic stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic and humoral effects of low-dose aspirin in treated and untreated essential hypertensive patients

Aspirin at low doses is used as an inhibitor of platelet aggregation and is frequently administered to essential hypertensive patients with arterial thrombotic complications. However, it is unknown whether aspirin can modify blood pressure values either in treated or untreated hypertensive patients, as described for other non steroidal anti-inflammatory drugs. Thus 30 patients. 10 with mild uncomplicated and untreated essential hypertension, 10 with essential hypertension under chronic treatment with captopril, 50 mg bid, and 10 with essential hypertension under chronic treatment with atenolol, 100 mg oid, received aspirin, 100 mg oid, and the corresponding placebo for one month, according to a double blind randomized cross-over design. At the end of each treatment, blood pressure, heart rate, generated serum thromboxane B2 and urinary excretion of thromboxane B2 and 6 keto prostaglandin F1 alpha and plasma renin activity were measured. Both in treated and untreated essential hypertensive patients, aspirin administration did not affect blood pressure, heart rate and urinary 6 keto prostaglandin F1 alpha, while it significantly reduced serum and urinary excretion of thromboxane B2 and plasma renin activity. In conclusion, while the present data confirm that low doses of aspirin selectively inhibit thromboxane B2 synthesis, they indicate that aspirin at 100 mg oid can be administered to treated and untreated essential hypertensive patients without any harmful effect on blood pressure values.

Vascular renin-angiotensin system and sympathetic nervous system activity in human hypertension

Experimental data indicate the existence of a vascular tissue renin-angiotensin system in several different vessels from various animal models. Active renin can be locally synthesized into the vessel wall or taken up from circulating plasma to produce vascular angiotensin II. Using the human forearm technique, we produced evidence indicating the release of active and inactive renin and of angiotensin II from the vessels of hypertensive patients. Moreover, the production of vascular angiotensin II seems to be strictly correlated to the circulating renin profile, suggesting the possibility that vascular renin might be at least partially taken up from plasma. To investigate a possible function of the vascular renin-angiotensin system, we studied its interaction with sympathetic neurotransmission in essential hypertensive patients. In line with animal studies, vascular angiotensin II increases the vasoconstriction induced by the stimulation of the sympathetic nervous system through the potentiation of noradrenaline release at a presynaptic level, and this effect seems to be mediated by beta-adrenoceptor activation. This facilitating effect on sympathetic neurotransmission exerted by vascular angiotensin II can be antagonized by both angiotensin II antagonists and angiotensin-converting enzyme inhibitors.

Indirect evidence for vascular uptake of circulating renin in hypertensive patients

To evaluate whether, in the forearm of hypertensive patients with different circulating renin profiles, local beta-adrenergic receptor-induced production of active renin, plasma renin activity, angiotensin I (Ang I), and angiotensin II (Ang II) was or was not related to the renin profile, we studied four groups of patients: 1) hypertensive patients with primary aldosteronism and suppressed circulating plasma renin activity values (0.15 +/- 0.1 ng Ang I/mL per hour; n = 7), 2) essential hypertensive patients with low (0.47 +/- 0.1 ng Ang I/mL per hour; n = 8) circulating plasma renin activity values, 3) essential hypertensive patients with normal (2.48 +/- 0.52 ng Ang I/mL per hour; n = 8) circulating plasma renin activity value, and 4) renovascular hypertensive patients with high circulating plasma renin activity values (4.16 +/- 2.1 ng Ang I/mL per hour; n = 10). Isoproterenol was infused into the brachial artery, and active renin, plasma renin activity, and Ang I and Ang II forearm balance (venous-arterial differences corrected for forearm blood flow by strain-gauge plethysmography) were measured. Despite a comparable vasodilation, beta-adrenergic stimulation failed to release active renin, plasma renin activity, and Ang I and Ang II in primary aldosteronism. It slightly increased them (except for Ang I) in low renin patients but determined a local production in normal renin and renovascular hypertensive patients. The individual increments in plasma renin activity and Ang II release induced by isoproterenol showed a correlation with the renin profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of sympathetic tone during dipyridamole test

Cardiac imaging with dipyridamole infusion has been proposed as an exercise-independent tool for the diagnosis of coronary artery disease. Dipyridamole acts through the accumulation of adenosine, which reduces sympathetic tone in vasomotor nuclei of the brainstem and inhibits norepinephrine release in noradrenergic neurons but also activates arterial chemoreceptors. The aim of this study was to assess whether dipyridamole administration (up to 0.84 mg/kg over 10 minutes, a dosage commonly employed for diagnostic testing) may modulate sympathetic activity either directly or indirectly through blood pressure reduction or myocardial ischemia, which may be evoked by dipyridamole infusion and represent two recognized sympathetic stimuli. Twenty patients were studied with infusion combined with two-dimensional echocardiography and 12-lead ECG monitoring. Blood pressure was recorded each minute by a cuff sphygmomanometer. In all patients, we obtained venous blood samples for epinephrine (an index of adrenomedullary catecholamine release) and norepinephrine (an index of neuronal activity) both in resting conditions and at peak dipyridamole, ie, at the first minute after termination of dipyridamole infusion in negative cases or in the presence of obvious ischemia in positive cases (ie, as soon as a regional ventricular dyssynergy or an ST segment depression greater than 0.1 mV appeared). Epinephrine and norepinephrine determinations were made by a high performance liquid chromatography (HPLC) method. After dipyridamole, there was a significant rise in norepinephrine, while epinephrine did not change significantly. Dipyridamole-induced percentage variations of norepinephrine from baseline were not significantly correlated with mean blood pressure changes (r = .1, p = ns) and were of a similar extent in patients with (n = 10) and without (n = 10) dipyridamole-induced ischemia (+68 vs +73 percent, p = ns). Dipyridamole administration provokes an activation of sympathetic tone which can be detected even in the absence of myocardial ischemia and is not related to blood pressure changes. The increased catecholamine release appears to be of neuronal rather than adrenomedullary origin.

Adenosine activates a vascular renin-angiotensin system in hypertensive subjects

In vitro data indicate that the activation of A2 adenosine receptors increases renin release by the accumulation of cyclic AMP. Because in human forearm vessels beta-adrenergic receptor stimulation causes the local release of renin and angiotensin II through the increase of cyclic AMP, we evaluated in six essential hypertensive subjects whether adenosine can release vascular angiotensin II. Adenosine was infused into the brachial artery at cumulatively increasing doses (0.5, 1.5, and 5 micrograms/100 ml forearm tissue per minute for 5 minutes each) during saline infusion and in the presence of the adenosine antagonist theophylline (100 micrograms/100 ml forearm tissue per minute for 15 minutes), while venous (ipsilateral deep forearm vein) and arterial (brachial artery) angiotensin II (picograms per milliliter) were measured at the end of each infusion period, and forearm angiotensin II net balance (picograms per minute) was calculated by venous-arterial differences corrected for forearm blood flow (strain-gauge venous plethysmography) and hematocrit. In control conditions, adenosine, at higher doses, caused a dose-dependent vasodilation and increased venous angiotensin II without affecting arterial values; therefore, the calculated angiotensin II net balance showed an adenosine-mediated dose-dependent release. Theophylline pretreatment blunted adenosine-mediated forearm blood flow increments and angiotensin II release. The local origin of angiotensin II was further confirmed in another group of six hypertensive subjects in whom the angiotensin converting enzyme inhibitor captopril, locally infused at the rate of 2.5 micrograms/100 ml forearm tissue per minute for 15 minutes, abolished the adenosine-mediated venous angiotensin II increments. Our data indicate that exogenous adenosine can stimulate the production of angiotensin II in the forearm vessels of hypertensive patients.

Atrial natriuretic factor in essential hypertension: echocardiographic and humoral correlates

Aim of this study was to assess the relationship between plasma concentration of atrial natriuretic factor (ANF) and its two-dimensional echocardiographic (left ventricular mass, left atrium diameter) and humoral (plasma renin and aldosterone) variables in essential hypertension (EH). We evaluated 32 patients with uncomplicated mild to moderate EH and 10 controls. They were studied in the supine position after 7 days of constant dietary sodium intake and were off therapy since at least 3 weeks. ANF values overlapped between EH patients and controls (27.8 +/- 11.5 vs. 19.5 +/- 7.4 pg/ml, p = NS). In EH, no significant correlation was found between ANF values and left ventricular mass (r = 0.29), left atrial diameter (r = 0.04), mean arterial blood pressure (r = 0.26), plasma renin activity (r = 0.00), and aldosterone (r = 0.26). In EH, ANF values overlapped between the 15 patients with hypertrophy and the 17 patients with normal ventricular mass: 30.3 +/- 17 vs. 25.6 +/- 10.6 pg/ms (p = NS). We conclude that there is a substantial overlap in plasma ANF values between mild to moderate uncomplicated EH and controls, and left ventricular hypertrophy is not a major independent stimulus to ANF release in EH.

Doxorubicin cardiotoxicity is associated with alterations of plasma levels of atrial natriuretic factor

In order to determine the involvement of the atrial natriuretic factor (ANF) in a model of drug-induced cardiomyopathy, the effects of a single or repeated doses of doxorubicin on plasma ANF levels were examined. Female Wistar rats were treated with doxorubicin at two different schedules: a single 10 mg/kg iv dose or multiple 3 mg/kg iv doses once a week for 3 weeks; control groups were given vehicle (isotonic saline, 0.9% NaCl) intravenously. ANF was assayed in plasma by a specific and sensitive radioimmunoassay method and cardiac function was evaluated by monitoring of ECG and hemodynamic parameters. In the doxorubicin single-dose study plasma ANF values were measured during a period of 6 hours after dosing and were found to be significantly decreased at the 180th (12.5 +/- 2.9 pg/ml) and 360th minute (19.4 +/- 1.2 pg/ml) after dosing, compared to vehicle-treated animals (35.1 +/- 5.7 and 37.9 +/- 4.1 pg/ml, 180 and 360th minute, respectively). Rats treated with multiple doses of doxorubicin showed a significant increase in plasma ANF levels at the 21st (88.3 +/- 7.7 pg/ml) and 31st day (61.0 +/- 14.3 pg/ml) of the study compared to vehicle-treated animals at the same time points (41.8 +/- 8.0 and 26.5 +/- 7.2 pg/ml, respectively). At the 42nd day plasma ANF concentration in doxorubicin-treated rats was not significantly different from vehicle-treated rats. In both studies ANF level changes occurred in the setting of acute or chronic doxorubicin-induced cardiac damage, as evidenced by alterations of hemodynamic and ECG parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular renin-angiotensin system and neurotransmission in hypertensive persons

The existence of a vascular renin-angiotensin system and its role in modulating sympathetic activity were evaluated in forearm arterioles of hypertensive individuals. Isoproterenol (0.03, 0.01, 0.3 microgram/100 ml/min for 5 minutes each; n = 5) was infused into the brachial artery, and active and inactive renin, angiotensin II, and norepinephrine forearm balance (venous-arterial differences corrected for forearm blood flow by strain-gauge plethysmography) were measured. Isoproterenol caused vasodilation and a dose-dependent active and inactive renin, angiotensin II, and norepinephrine outflow, an effect blunted by propranolol (10 micrograms/100 ml/min). To evaluate the role of local angiotensin II on beta-mediated norepinephrine overflow, the experiment was repeated with captopril (2.5 micrograms/100 ml/min for 10 minutes; n = 5), which abolished angiotensin II release and significantly reduced norepinephrine overflow. To test whether angiotensin II facilitates both prejunctional norepinephrine release and its postjunctional action, we evaluated the effect of exogenous angiotensin II, infused into the brachial artery at low concentrations (0.001 microgram/100 ml/min), on forearm vasoconstriction and norepinephrine release induced by endogenous sympathetic activation (application of a lower body negative pressure: -10 and -20 mm Hg for 5 minutes, n = 10) and on the vasoconstrictor effect of local norepinephrine (0.0015, 0.005, 0.015, 0.05, 0.15 micrograms/100 ml/min for 3 minutes each; n = 6). Although angiotensin II increased the vasoconstricting effect and the norepinephrine release induced by lower body negative pressure, it failed to affect norepinephrine-mediated vasoconstriction. Our data indicate the existence in hypertensive individuals of a vascular renin-angiotensin system that seems to modulate sympathetic activity through the presynaptic facilitation of norepinephrine release.

Active and inactive renin in human forearm of hypertensive patients

Although many in vitro and animal studies indicate the existence of a local renin--angiotensin system, data regarding its physiological role are quite controversial, and moreover, evidence suggesting inactive and active renin release from vascular tissue in vivo is lacking both in animal and humans. The aim of our study was to evaluate whether beta-adrenoceptor stimulation, a well-known stimulus to renin production, through isoproterenol might cause local renin production from vessels of the forearm of hypertensive patients. Drugs were infused into the brachial artery at systemically ineffective rates, while forearm blood flow (FBF, venous plethysmography), mean intra-arterial pressure, and heart rate were monitored throughout. Active and inactive vessel renin production was measured by calculating venous-arterial (V-A) differences by simultaneous sampling from brachial artery and an ipsilateral deep vein. Active renin (PRA) and total renin (Sepharose bound trypsin activation) were measured by radioimmunoassay while inactive renin was calculated as the difference between total and active renin. V-A differences were corrected for FBF to calculate renin extraction or production. In a group of 10 patients, isoproterenol, which was infused at increasing cumulative rates (0.03, 0.1, 0.3 micrograms.100 mL-1 forearm tissue.min-1 for 5 min each), caused a dose-dependent increment in FBF that was blunted by intra-arterial propranolol (n = 5) pretreatment (10 micrograms.100 mL-1 forearm tissue.min-1 for 10 min). beta-Adrenoceptor stimulation caused a dose-dependent outflow of both active and inactive renin, an effect antagonized by propranolol. In conclusion, our data represent the first evidence in humans of tissue active and inactive renin production in the forearm vascular bed.

Dipyridamole-induced myocardial ischaemia increases ANF release in man

Atrial natriuretic factor (ANF) release is modulated by several haemodynamic factors, including ventricular and atrial wall stretch. Dipyridamole infusion, which is commonly used as a pharmacological stressor in patients with coronary artery disease, can acutely increase ventricular and atrial pressure via myocardial ischaemia. The aim of this study was to assess whether dipyridamole infusion (up to 0.84 mg kg-1 over 10') can affect ANF release in man. Nineteen patients (13 men, 6 women) with a history of chest pain were studied. Their drug regimen was interrupted and instead they were administered a dipyridamole infusion, combined with two-dimensional echocardiography and 12-lead ECG monitoring. Plasma ANF was measured by RIA while the patients rested, and after dipyridamole infusion. Eight patients had no evidence of myocardial ischaemia, as measured by electrocardiographic and/or echocardiographic criteria, during dipyridamole infusion: among them, ANF values were similar while they were at rest and at peak dipyridamole administration (23.9 +/- 9.5 vs 23.4 +/- 6.9 pg ml-1, P = ns). Eleven patients had dipyridamole-induced transient ischaemia (regional ventricular dyssynergy and/or ST segment depression): among them, ANF values rose significantly at peak dipyridamole administration (31.8 +/- 13.8 vs 65.5 +/- 36.4, P less than 0.01). We conclude that dipyridamole infusion does not increase ANF release in man in the absence of ischaemia. The induction of myocardial ischaemia acutely increases ANF release, probably through a rise in ventricular and atrial wall stress.

An atrial natriuretic factor analogue at low doses attenuates forearm reflex vasoconstriction to cardiopulmonary receptor deactivation in patients with hypertension

Contrasting data exist about a possible modulation of the autonomic function by atrial natriuretic factor (ANF) in human beings, particularly at low, biologically, significant concentrations. We have evaluated that possibility by increasing plasma ANF levels through the infusion of a synthetic analogue (WY-47,663, anaritide) in five male patients with mild to moderate uncomplicated hypertension. Nonhypotensive lower body negative pressure (-10 mm Hg x 5 min) was used to selectively deactivate cardiopulmonary receptors and to stimulate sympathetic efferent tone reflexogenically. ANF was given at either a low rate (0.005 micrograms/kg/min x 60 min, which was previously shown to increase plasma ANF in a range compatible with physiologic stimuli) or at a high rate (0.05 micrograms/kg/min x 60 min, each). Administration of ANF was preceded and followed by vehicle infusion (Haemacell x 30 min). Forearm blood flow (venous plethysmography), intraarterial blood pressure, and heart rate were monitored continuously, and venous immunoreactive ANF, plasma renin activity, aldosterone level, and venous hematocrit were measured at the end of both control and infusion periods. Arterial norepinephrine values, an indirect index of sympathetic discharge, were measured at rest and during lower body negative pressure conditions. Graded systemic ANF infusion increased immunoreactive ANF and venous hematocrit, decreased aldosterone level and plasma renin activity, whereas resting norepinephrine levels, blood pressure, and heart rate did not change. Lower body negative pressure decreased forearm blood flow during vehicle infusion, but it lost its vasoconstrictor effect during infusion of ANF. To identify the site of that inhibitory action, ANF was also infused into the brachial artery at rates that raised local but not systemic levels of immunoreactive ANF.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor as a vasodilator agent in hypertensive patients

To investigate the role of Atrial Natriuretic Factor (ANF) in modulating arteriolar tone in hypertension, a synthetic 25 AA human ANF-analogue (anaritide) was infused intraarterially in the forearm vascular bed of five patients with mild hypertension. A dose-dependent increase in blood flow (plethysmographic technique) was seen at rates covering a thousand-fold range (0.008, 0.08, 0.8, 8.0 micrograms/dl tissue/min x 15 minutes each). At the lowest infusion rate, the forearm blood flow increment was associated with changes in local venous ANF concentrations comparable with those reported during biological stimuli in hypertensive man and consistent with an ANF physiologic role in forearm arterioles of hypertensive patients. However, at local venous concentrations greater than 1000 pg/ml, ANF did not relax forearm vessels by more than about one-fourth of the total forearm vasodilator capacity (as assessed through a maximally active ischemic stimulus). These data confirm the low potency of ANF as an endogenous vasodilator, although vasodilator potency is not a necessary requirement for physiologic systems involved in the regulation of muscular vascular tone. Systemic arterial pressure, heart rate, and contralateral flow did not change during the study in spite of the markedly increased peripheral ANF levels recirculating from the local forearm administration. This behavior indicates that arteriolar vasodilation is apparently not the main mechanism of action of ANF on systemic hemodynamics in hypertensive patients.

The influence of dopamine-1 receptor blockade on the humoral and renal effects of low-dose atrial natriuretic factor in human hypertensives

To test whether dopaminergic mechanisms can modulate the humoral and renal effects of atrial natriuretic factor (ANF), seven untreated, mildly hypertensive patients without complications were given a placebo (saline for 60 min) followed by a low dose of ANF (0.005 microgram/kg per min), or D-sulpiride (0.05 mg/kg per min), a specific dopamine-1 antagonist, or ANF + D-sulpiride at the same doses, for 60 min. The sequence of the three treatments was random, with a 72-h interval between treatments. The ANF infusion, which increased plasma ANF within the physiological range, significantly increased urinary sodium excretion, fractional sodium excretion and haematocrit; it reduced plasma aldosterone and tended to reduce plasma renin activity without changing blood pressure, the heart rate, renal plasma flow or the glomerular filtration rate. D-Sulpiride, when given alone, significantly increased mean blood pressure and reduced absolute and fractional sodium excretion without changing the heart rate, glomerular filtration rate, renal plasma flow, haematocrit, plasma renin activity or plasma aldosterone. When infused with D-sulpiride, ANF did not change absolute or fractional sodium excretion or haematocrit. This study provides evidence that dopaminergic mechanisms play a role in the natriuretic and plasma volume effects of a synthetic human ANF analogue infused at a low dose in patients with essential hypertension.

Low dose atrial natriuretic factor in primary aldosteronism: renal, hemodynamic, and vascular effects

Whether atrial natriuretic factor (ANF) plays a physiological role in primary aldosteronism has yet to be determined. In the present study, the renal, hemodynamic, humoral, and vascular effects of a synthetic (WY-47663) human analogue were studied in five water-loaded (15 ml H2O/kg) patients with adenomatous primary aldosteronism, a salt-sensitive, low renin, volume-expanded syndrome. ANF was infused for 3 hours at a low rate (0.005 micrograms/kg/min), which approximately doubled circulating immunoreactive ANF. Glomerular filtration rate and renal blood flow (inulin and para-aminohippurate clearance) remained stable, but sodium excretion increased significantly suggesting a dissociation between renal hemodynamics and natriuresis as well as a direct inhibitory effect on tubular sodium reabsorption by ANF. Intra-arterial diastolic blood pressure, heart rate, forearm blood flow (plethysmographic method), and arterial plasma norepinephrine did not change, but systolic blood pressure declined and hematocrit rose suggesting plasma volume contraction by ANF. Plasma aldosterone levels were unchanged indicating a loss of ANF-mediated aldosterone inhibition, possibly related to qualitative or quantitative alterations of ANF receptors in tumoral adrenal tissue. Infusion of the analogue into the brachial artery was at a rate of 0.005 micrograms/dl forearm tissue/min x 30 minutes, which also doubled local immunoreactive venous ANF concentrations and vasodilated forearm arterioles. These data suggest a physiological role for ANF in modulating body fluid volume even in human primary aldosteronism.

Increased protein C and fibrinopeptide A concentration in patients with angina

Protein C and fibrinopeptide A (FpA) levels in plasma were measured in 30 controls and in two groups of patients with angina. The first group was formed by 27 patients suffering from spontaneous ischemic attacks (active angina). The second one was formed by patients who had previously suffered from angina, but were free from myocardial ischemic attacks for at least one month (inactive angina). Protein C (measured by electroimmunoassay) and FpA (radioimmunoassay) were higher than controls in both groups but were significantly higher in patients with active angina than in patients with inactive angina. A clear trend toward a linear correlation existed between protein C and FpA levels, though it did not reach the statistical significance. These results confirm a significant involvement of blood clotting system in ischemic heart disease and specially in active angina.

Platelet synthesis of cyclooxygenase and lipoxygenase products in type I and type II diabetes

In 24 type I and 22 type II diabetic patients without vascular complications and in 25 controls platelet thromboxane A2 (TxA2) and prostaglandin E2 (PGE2) production (by radioimmunoassay-RIA) and 1-14C arachidonic acid (AA) metabolism (by high pressure liquid chromatography-HPLC) after thrombin stimulation were studied. Platelets both from type I and type II diabetics generated larger amounts of TxB2 (p less than 0.001) and PGE2 (p less than 0.005) than controls, independently of the presence of retinopathy. No significant differences in platelet AA uptake or metabolism via the cyclooxygenase (CO) route, after thrombin stimulation (5 NIH U/ml), were observed in diabetic patients: lipoxygenase metabolites were found to be slightly, but significantly decreased. A positive linear relationship (r = 0.64, p less than 0.001) was found between HbA-1c and TxB2 production, but not with fasting plasma glucose. These results indicate that metabolic alterations can affect platelet function independently of vascular complications. The absence of alterations in intraplatelet 1-14C AA metabolism via CO, in the presence of increased TxB2 and PGE2 production from endogenous AA, suggests that the activation of CO is not the only possible mechanism of platelet activation and that probably an increased availability of platelet AA plays an important role in the enhanced platelet aggregation commonly found in diabetics.

The interference of indomethacin and of imidazole salicylate on blood pressure control of essential hypertensive patients treated with atenolol. Preliminary report

To evaluate whether imidazole salicylate, a recently developed NSAID, can interfere with the antihypertensive effect of atenolol and to compare its action with that of indomethacin, 9 essential hypertensives, while on prolonged (more than 1 month) treatment with atenolol (100 mg qd) received, according to a double-blind cross-over study, imidazole salicylate (750 mg t.i.d.) or indomethacin (50 mg b.i.d. plus a placebo tablet) for 1 week, reverting the treatment after a 2-week wash-out period. While indomethacin addition significantly increased blood pressure, when compared to atenolol alone, imidazole salicylate did not change it. These data show that imidazole salicylate, unlike indomethacin, does not reduce the antihypertensive effect of atenolol.

Altered intraplatelet arachidonic acid metabolism during the acute state of unstable angina

Thromboxane A2 (TxA2) generation and 1-14C arachidonic acid (AA) metabolism by platelets (stimulated with thrombin) were studied in vitro in 16 patients with unstable angina both during the acute and chronic inactive phase of the angina. Eight patients with stable effort angina and 21 controls were also investigated. In acute unstable angina 1-14C AA metabolism was significantly increased through cyclooxygenase pathway resulting in a higher selective TxA2 generation than in stable effort angina and in controls (p less than 0.01). No differences were found between patients with stable effort angina and controls. The alterations in AA metabolism were no longer found when patients reverted to the inactive phase of angina. TxA2 generation by platelets was independent of the number of the daily ischemic attacks (r = 0.17, ns) in patients with unstable angina. Present results indicate that an altered intraplatelet AA metabolism leading to the increased TxA2 synthesis occurs simultaneously with the conversion of angina from the chronic to the acute phase.

Factors influencing platelet aggregation in whole blood

In order to evaluate the interference of blood cells on platelet aggregation, spontaneous platelet aggregation (SPA), ADP, and collagen-induced platelet aggregation were investigated in whole blood by the impedance method and in platelet-rich plasma (PRP) by densitometric and impedance aggregometers. Stirring of the sample induced a significant decrease of neutrophils (P less than 0.001) but no changes of red blood cell (RBC) and platelet count. After collagen addition, a further decrease of neutrophils was observed, while RBC count was unmodified. The occurrence of SPA was not different in whole blood and in PRP. Platelet number and hematocrit did not affect either spontaneous or collagen-induced aggregation. A significant linear relation (r = -0.60, P less than 0.01) between neutrophil count and collagen whole blood platelet aggregation was found. Collagen- and ADP-induced aggregation were significantly higher and lower, respectively, in whole blood than in PRP using the densitometric method. No differences were observed in SPA and collagen platelet aggregation according to age and sex.

Hemodialysis leukopenia and complement function with different dialyzers

The relationship between leukopenia and the complement system during hemodialysis was re-examined by studying not only the in vivo effects of four different dialyzer membranes (cellulose hydrate, cuprophan, cellulose acetate, and polyacrilonitrile) on leukocyte counts and complement levels, but especially by investigating the effects of these membranes on complement function in vitro. Whereas from in vivo studies no definite conclusions could be drawn, in vitro investigations provided clear-cut information. When more sophisticated technical approaches were undertaken, it became evident that hemodialysis leukopenia has to be thought of in terms of chemotactic factor generation. In fact, a strict correlation was demonstrated between the degree of leukopenia induced by the dialyzers tested and the ability of the relative membrane to generate chemotactic activity in vitro. Moreover, the previously observed ability of polyacrilonitrile membrane to induce a decrement in complement function was due to the ability of polyacrilonitrile to adsorb complement activity and did not correspond to effective complement consumption. This finding explained why polyacrilonitrile dialysis is not accompanied by a decrease in circulating granulocytes. Taken together, our data strongly point to a pivotal role of complement system in the pathogenesis of hemodialysis leukopenia.

Ticlopidine activity on platelet function in patients with enhanced platelet aggregation. A short-term crossover study

In a single-blind crossover study, the effect of ticlopidine (250 mg t.i.d.) on platelet function was investigated in 16 patients, with enhanced platelet aggregation, before treatment, on the third and seventh day of treatment with the drug or the placebo. Bleeding time was significantly lengthened by ticlopidine administration. Platelet aggregation, both in vivo and in vitro, was significantly inhibited during the week on ticlopidine. Beta-thromboglobulin concentration was on an average significantly decreased. The inhibition by PGI2 of platelet aggregation by PGD2 was slightly but not significantly increased. Platelet TxB2 production after stimulation with thrombin was unchanged during ticlopidine administration, whereas conversion of exogenous arachidonic acid into TxB2 was slightly but significantly reduced. The present results confirm that ticlopidine acts in vivo as a powerful antiaggregating agent. The antiaggregating activity seems to be due to an interference of ticlopidine with platelet membrane and, as a consequence, with various platelet membrane receptors and activities.

Increased fibrinopeptide A formation and thromboxane A2 production in patients with ischemic heart disease: relationships to coronary pathoanatomy, risk factors, and clinical manifestations

In 98 patients with ischemic heart disease (IHD), independent of their clinical status (previous myocardial infarction, spontaneous angina or effort angina), a hypercoagulable state (indicated by significant elevation of fibrinopeptide A plasma level) and an increased platelet biologic activity were observed. Moreover, plasma fibrinopeptide A concentration and platelet aggregation were remarkably higher in patients with frequently occurring spontaneous clinical manifestations (active disease) than in IHD patients with relatively quiescent symptoms. Abnormalities of blood clotting and platelet changes were not significantly altered by the presence of severity of coronary angiographic fixed obstruction in IHD. Multiple regression analysis indicated that hypercoagulability and increased platelet biologic activity were not a consequence of differences in risk factor patterns in IHD patients compared to control subjects.

Early Changesof the Endothelial Anthrombotic Properties in Cholesterol fed Rabbits. II-Changes of Heparansulphatf and Other Gags

Sulphated mucopolysaccharides are synthetized by the endothelial cells and they occurr associated with the external cell surface and probably play a role in the non-thrombogenie properties of the endothelial layer. Heparansulphate (H.S.), chondroitin-6-sulphate (Ch-6-S) and hyaluronic acid (H.A.) concentrations were investigated by electrophoresis on Titan III zip zone cellulose acetate plate. Uronic acids were determined according to Dische. After 7 days of diet a significant decrease (m.v. -63%, P<0.001) of H.S..H.A. and Ch-6-S could be observed without changes of their reciprocal concentrations. After 14 days H.S., H.A. and Ch-6-S increased and no differences were observed in comparison with control rabbits. However after 28 days of diet H.S., H.A. and Ch-6-S showed a further and more pronounced decrease (m.v. -7%. P<0.001). Uronic acids showed changes tightly similar to those of sulphated glycosaminoglycans.

Modulation by Dipyridamole of the Arachidonic Acid Metabolic Pathway in Platelets an in vivo and in vitro Study

Dipyridamole is a useful antiplatelet agent in specific clinical conditions, but its effects on TxEL production by platelets are now being debated, Resting platelets from patients with 1.5-2 fig/ml serum dipyridamole (spectrofluorimetric assay). administered by venous infusion or by oral route, showed an increased concentration (m.v. +60% P<0.001) of cAMP (radiometric assay). After stimulation with thrombin (5U/ml) platelets produced a significantly decreased amount of TxB(m.v. -60%, F< 0.001) (radioimmunoassay with antibody kindly supplied by Doctor J.B. Smith, Philadelphia). However also after stimulation with arachidonic acid (A.A.) 1 mM TxB production was decreased(m.v. -50%, P<0.001). The incubation of control platelets with different concentrations of dipyridamole (0.5, 1 and 2 μg/ml) for 20 min at 37°C resulted in an increase of cAMP and in a decrease of TxB, production after stimulation with thrombin and with A.A.. These results indicate that dipyridamole is endowed with direct antiaggrega= ting activity caused by a decreased production of TxB2. This in tum seems due to an inhibitory modulating effect of cAMP on arachidonic acid cyclo-oxygenation. However our findings do not rule out an inhibitory effect also on phospholipase A2.

Early Changes of the Emxtthelial Aotithrokibotic Properties in Cholesterol Fed Rabbits. I-Changes of A.D.P.-Ase and 5'-N.T.-Ase Activities

Severe endothelial damage is usually associated to developing atherosclerotic lesions in rabbits. However the early functional endothelial changes are poorly known, specially as far as the endothelial antithrombotic mechanisms are concerned.

In cholesterol (1 g/die) fed rabbits the endothelial aortic A.D.P.-ase and 5’-N.T.-ase activities (according to Lieberman 1977) were investigated after 7.14 and 28 days of diet. A.D.P.-ase and 5'-N.T.-ase changes occurred very early. A.D.P.-ase activity decreased already after 7 days of diet (m.v. -45%, P<0.COl) in comparison with control rabbits, but it did not show any further decrease after 14 and 24 days. A decrease of 5'-N.T.-ase activity (m.v. -36%, P<0.01) occurred only after 14 days of diet and it did not furtherly decrease after 28 days. These findings suggest that in cholesterol induced atherosclero -sis an early impairment of the antiaggregating properties of the endothelial wall occurs, but it does not increase for the length of time of our observation.