An Overview of Chronic Kidney Disease Pathophysiology: The Impact of Gut Dysbiosis and Oral Disease

Chronic kidney disease (CKD) is a severe condition and a significant public health issue worldwide, carrying the burden of an increased risk of cardiovascular events and mortality. The traditional factors that promote the onset and progression of CKD are cardiometabolic risk factors like hypertension and diabetes, but non-traditional contributors are escalating. Moreover, gut dysbiosis, inflammation, and an impaired immune response are emerging as crucial mechanisms in the disease pathology. The gut microbiome and kidney disease exert a reciprocal influence commonly referred to as "the gut-kidney axis" through the induction of metabolic, immunological, and endocrine alterations. Periodontal diseases are strictly involved in the gut-kidney axis for their impact on the gut microbiota composition and for the metabolic and immunological alterations occurring in and reciprocally affecting both conditions. This review aims to provide an overview of the dynamic biological interconnections between oral health status, gut, and renal pathophysiology, spotlighting the dynamic oral-gut-kidney axis and raising whether periodontal diseases and gut microbiota can be disease modifiers in CKD. By doing so, we try to offer new insights into therapeutic strategies that may enhance the clinical trajectory of CKD patients, ultimately advancing our quest for improved patient outcomes and well-being.

Prevalence of Cardiovascular Risk Factors and Related Medical and Lifestyle Interventions Among Italian Cardiovascular Specialists: A Proof-of-Concept Study

INTRODUCTION

Physicians and researchers in the cardiovascular field are constantly engaged in the promotion of guidelines-directed preventive measures, but whether they are themselves adherent to the same recommendations was only sporadically examined.

AIM

To assess awareness of self-exposure to cardiovascular risk factors and related management among cardiovascular specialists.

METHODS

During the National Conference of the Italian Society of Hypertension (October 2022), a pilot observational study on consecutive volunteer cardiovascular specialists was conducted. Participants underwent standard sitting and standing blood pressure (BP) measurements and answered a questionnaire regarding modifiable/non modifiable cardiovascular risk factors and related treatments. Based on self-declarations and actual measurements, BP was classified as optimal, normal, high-normal BP, and new hypertension in untreated participants, and as treated/untreated pre-existing hypertension. Controlled hypertension was defined as BP < 140/90 mmHg; age-adjusted lower targets were also applied, according to guidelines.

RESULTS

In total, 62 participants (30 F, mean age 43.2 ± 14.8 years) were enrolled; 79% reported regular physical activity; 53% of women and 38% of men were on a low-salt diet. After smoke (19.4%), dyslipidemia was the second most common risk factor (17.7%), often occurring with high BP (26.3%) and left untreated (36.7%). Pre-existing hypertension (11.3%) was often uncontrolled (57.1%) and associated with non-adherence to guidelines-directed lifestyle recommendations. About one in 12 participants was unaware of having high measured BP values.

CONCLUSIONS

Despite the specific professional exposure, a margin for improvement in self cardiovascular risk factors awareness and management remains in this exploratory sample of cardiovascular specialists. This pilot research anticipates forthcoming, larger studies during national and international conferences.

Association between metabolic syndrome components and gingival bleeding is women-specific: a nested cross-sectional study

BACKGROUND

Metabolic syndrome (MetS) is a cluster of atherosclerotic risk factors that increases cardiovascular risk. MetS has been associated with periodontitis, but the contribution of single MetS components and any possible sexual dimorphism in this relation remain undetermined.

METHODS

Using the third National Health and Nutrition Examination Survey (NHANES III), we performed a nested cross-sectional study to test whether individuals aged > 30 years undergoing periodontal evaluation (population) exposed to ≥ 1 MetS component (exposure) were at increased risk of bleeding/non-bleeding periodontal diseases (outcome) compared to nonexposed individuals, propensity score matched for sex, age, race/ethnicity, and income (controls). The association between MetS components combinations and periodontal diseases was explored overall and across subgroups by sex and smoking. Periodontal health status prediction based on MetS components was assessed.

RESULTS

In total, 2258 individuals (n. 1129/group) with nested clinical-demographic features were analyzed. Exposure was associated with gingival bleeding (+ 18% risk for every unitary increase in MetS components, and triple risk when all five were combined), but not with stable periodontitis; the association was specific for women, but not for men, irrespective of smoking. The only MetS feature with significant association in men was high BP with periodontitis. CRP levels significantly increased from health to disease only among exposed women. MetS components did not substantially improve the prediction of bleeding/non-bleeding periodontal disease.

CONCLUSION

The observed women-specific association of gingival bleeding with single and combined MetS components advances gender and precision periodontology. Further research is needed to validate and expand these findings.

Oral health as a modifiable risk factor for cardiovascular diseases

Cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality worldwide with a high socioeconomic burden. Increasing evidence supports a convincing connection with increased cardiovascular risk of periodontal diseases (PD), a group of widespread, debilitating, and costly dysbiotic relapsing-remitting inflammatory diseases of the tissues supporting the teeth. Herein, we ensembled the best available evidence on the connection between CVDs and PD to review the recently emerging concept of the latter as a non-traditional risk factor for CVDs. We focused on oral dysbiosis, inflammation-associated molecular and cellular mechanisms, and epigenetic changes as potential causative links between PD and CVDs. The available evidence on the effects of periodontal treatment on cardiovascular risk factors and diseases was also described.

Hypertension and periodontitis: A joint report by the Italian society of hypertension (SIIA) and the Italian society of periodontology and implantology (SIdP)

An accumulating body of evidence supports an independent association between high blood pressure (BP) and periodontitis, possibly mediated by low-grade inflammation. This joint report by the Italian Society of Hypertension (SIIA) and the Italian Society of Periodontology and Implantology (SIdP) working group on Hypertension and Periodontitis (Hy-Per Group) provides a review of the evidence on this topic encompassing epidemiology, biological plausibility, relevance, magnitude, and treatment management. Consensus recommendations are provided for health professionals on how to manage BP in individuals showing signs of poor oral health. In summary, (1) large epidemiological studies highlight that individuals with periodontal diseases have increased risk for high/uncontrolled BP independent of confounders; (2) mechanistically, low-grade inflammation might have a causal role in the association; (3) BP profile and control might benefit from periodontal treatment in pre-hypertensive and hypertensive individuals; (4) oral health status should be evaluated as a potential risk factor for high/uncontrolled BP, and effective oral care should be included as an adjunct lifestyle measure during hypertension management. Further research is needed to optimize BP management in individuals with poor oral health.

Impact of 2021 ESC Guidelines for Cardiovascular Disease Prevention on Hypertensive Patients Risk: Secondary Analysis of Save Your Heart Study

INTRODUCTION

Cardiovascular diseases (CVD) are a leading cause of death worldwide, and several modifiable and unmodifiable risk factors contribute to this burden of disability and mortality. Thus, effective cardiovascular prevention relies on appropriate strategies to control risk factors within the frame of unmodifiable traits.

METHODS

We conducted a secondary analysis of treated hypertensive adults aged ≥ 50 years enrolled in Save Your Heart. CVD risk and hypertension control rates based on the 2021 updated European Society of Cardiology guidelines were evaluated. Comparisons with previous standards in terms of risk stratification and hypertension control rates were performed.

RESULTS

Among the 512 patients evaluated, with the application of the new parameters for fatal and non-fatal cardiovascular risk assessment, the proportion of individuals at high or very high risk rises from 48.7 to 77.1% of cases. A trend towards lower hypertension control rates was observed based on 2021 European guidelines compared with the 2018 edition (likelihood estimate for difference: 1.76%, 95% CI - 4.1 to 7.6%, p = 0.589).

CONCLUSIONS

In this secondary analysis on the Save Your Heart study, the application of the new parameters reported in the European Guidelines for Cardiovascular Prevention 2021 showed a hypertensive population with a very high probability of encountering a fatal or non-fatal cardiovascular event due to failure to control risk factors. For this reason, a better management of risk factors must be the main goal for the patient and all the involved stakeholders.

Home oral hygiene is associated with blood pressure profiles: Results of a nationwide survey in Italian pharmacies

AIM

Periodontal diseases are associated with cardiovascular risk factors/diseases, and whether home oral hygiene practices are inversely related to the same conditions could carry relevant practical implications. We investigated the association of home oral hygiene habits with hypertension.

MATERIALS AND METHODS

During World Hypertension Day 2020, a nationwide cross-sectional survey was conducted on volunteers ≥18 years at 733 Italian pharmacies. Participants underwent standardized blood pressure (BP) measurement and answered a questionnaire on cardiovascular risk factors, oral health status, and home oral hygiene habits (toothbrushing daily frequency and manual/electric toothbrush). The association between home oral care habits and BP was assessed using multivariate logistic regression. Interactions between exposures and outcome were formally tested.

RESULTS

Among the 4506 participants (44.8% males, 66.1 ± 37.8 years), 47.6% reported brushing ≥3 times/day and 23.4% declared using the electric toothbrush. Brushing ≥3 versus &lt;3 times/day and use of electric versus manual toothbrush were associated with 19% (odds ratio [OR]: 0.81, 95% confidence interval [CI] 0.70-0.94) and 28% (OR: 0.72, 95% CI 0.61-0.85) lower odds of hypertension, respectively. No significant additive interaction was observed in the association of exposures with the outcome.

CONCLUSIONS

Regular daily brushing and electric toothbrushing are associated with a better BP profile in a real-world context. Future interdisciplinary research is warranted to test these findings.

Iron deficiency in heart failure: diagnosis and clinical implications

Iron deficiency is a widely prevalent finding in patients with heart failure, observed on average in 50% of outpatients and up to 80% of acute patients, regardless of the ejection fraction and the presence of anaemia, being an independent predictor of worst functional capacity and reduced survival. The definition of iron deficiency in heart failure considers the state of chronic inflammation that characterizes the pathology, recognizing a discriminating role for transferrin saturation. The studies conducted so far, which focused on the patient with heart failure with at least moderately reduced ejection fraction, have shown clinical benefit with intravenous supplementation of ferric carboxymaltose in terms of functional capacity, quality of life, laboratory markers of disease and inflammation, and possible reduction of re-hospitalizations, but not in terms of mortality. Based on this evidence, guidelines recommend intravenous ferric carboxymaltose in decompensated and iron-deficient patients, while research is at work to investigate the clinical impact of supplementation in contexts not yet examined, such as that of decompensation in patients with heart failure and preserved ejection fraction.

Immune-mediated inflammatory diseases after anti-SARS-CoV-2 vaccines: new diagnoses and disease flares

Objective

New-onset immune-mediated inflammatory diseases (IMIDs) and flares of pre-existing IMIDs have been reported following anti- SARS-CoV2 vaccination. Our study aimed at describing a retrospective cohort of patients developing new-onset IMIDs or flares of known IMIDs within 30 days after any anti-SARS-CoV2 vaccine dose.

Methods

We evaluated clinical records of all inpatients and outpatients referring to our institution between February 2021 and February 2022 with any clinical manifestations. We then selected those having received any anti-SARS-CoV2 vaccine dose within the prior 30 days and classified them as having or not a previous IMID according to predefined criteria. We recorded new-onset IMIDs or flares of known IMIDs and investigated any relationship with demographic, clinical and serological variables.

Results

153 patients that received any anti-SARS-CoV2 vaccine dose within the previous 30 days were included of which 45 (29%) already had a diagnosis of IMID while 108 (71%) had no previously diagnosed IMID. 33 (30%) of the 108 patients, were diagnosed with a new-onset IMID. Pericarditis, polymyalgia rheumatica and vasculitis were the most frequent conditions. Among the 45 patients that already had an IMID, disease flare was the reason for referral in 69% of patients. Patients with an IMID flare had a lower number of comorbidities and tended to be younger compared with those who developed other conditions after anti-SARS-CoV2 vaccination.

Conclusion

We provided a retrospective overview of a cohort of patients who developed new-onset IMIDs or flares of known IMIDs within 30 days after any dose of anti-SARS-CoV2 vaccine. While vaccination campaigns proceed, postvaccination surveillance programmes are ongoing and hopefully will soon clarify whether a causal relationship between vaccines and new-onset/flares of IMIDs exists.

World Hypertension Day 2021 in Italy: Results of a Nationwide Survey

Introduction

Hypertension is the biggest contributor to the global burden of cardiovascular diseases and related death, but the rates of hypertension awareness, treatment, and control remain largely perfectible.

Methods

During the XVII World Hypertension Day (May 17th, 2021), a nationwide cross-sectional opportunistic study endorsed by the Italian Society of Hypertension was conducted on volunteer adults ≥ 18 years to raise awareness of high blood pressure (BP). A questionnaire on major demographic/clinical features (sex, age, employment, education, BP status awareness, hypertension family/personal history, antihypertensive medications use) and BP measurement habits (≥1 BP measurement in the previous month/week) was administered. Due to the ongoing SARS-CoV-2 pandemic, BP was measured with standard procedures in a subset of participants (24.4%).

Results

A total of 1354 participants (mean age 56.3 ± 15.3 years; 57.3% women; mean BP: 131.2 ± 17.5/81.6 ± 10.5 mmHg; 42.3% self-declared hypertensive; 41.4% on antihypertensive medications) were enrolled; 73.6% declared being aware of their BP status. Among treated individuals with measured BP, 26.9% showed BP levels within the predefined therapeutic goals. Interestingly, BP status awareness rates were the highest among individuals with uncontrolled hypertension (85.1%) and the lowest among those with normal measured BP (54.4%).

Conclusions

This survey provides an updated insight into hypertension awareness and control in a setting of daily clinical practice, emphasizing the centricity of patients in the therapeutic alliance for a successful reduction of cardiovascular risk.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40292-022-00519-4.

Analysis of Aspirin Use and Cardiovascular Events and Mortality Among Adults With Hypertension and Controlled Systolic Blood Pressure

This cohort study investigates the association of aspirin use with risk of cardiovascular events among adults with hypertension and controlled systolic blood pressure.

Humoral Immune Response to COVID-19 Vaccination in Hemodialysis Patients: A Retrospective, Observational Case-Control Pilot Study

INTRODUCTION

Coronavirus 2 disease is associated with increased mortality and morbidity in chronic hemodialysis patients METHODS: A retrospective, observational case-control pilot study was conducted on consecutive hemodialysis outpatients (cases) and control group of individuals with preserved renal function. Complete SARS-CoV-2 vaccination with BNT162b2 mRNA vaccine, followed by determination of serum antibodies after the second dose, were required from participants in both groups. Previous COVID-19 was an exclusion criterium.

RESULTS

21 hemodialysis patients (M:F = 13:8, mean age 67.5 ± 13.4) and 16 controls without chronic kidney disease (M:F = 4:12, mean age 46.8 ± 12.7) were included. Hemodialysis patients had lower mean titers of serum antibodies to the SARS-CoV-2 spike antigen compared with controls (492.39 vs 1901.20 IU/mL, respectively; p < 0.001), a finding that was confirmed in the age-matched analysis on 18 participants (580.8 vs 1836.4 IU/mL, p = 0.006).

CONCLUSIONS

This study supports the finding of hyporesponsiveness to mRNA vaccination among hemodialysis patients.

Access to dental care and blood pressure profiles in adults with high socioeconomic status

Background

Reduced access to dental care may increase cardiovascular risk; however, socioeconomic factors are believed to confound the associations. We hypothesized that the relation persists despite economic wellness and high education, with reduced access to dental care affecting cardiovascular risk at least in part through its effect on blood pressure (BP), possibly mediated by systemic inflammation.

Methods

We first assessed the sociodemographic and clinical characteristics related to last dental visit timing (≤ or >6 months; self‐reported) using national representative cross‐sectional data. Then, the association of last dental visit timing with clinic BP was selectively investigated in highly educated, high income participants, further matched for residual demographic and clinical confounders using propensity score matching (PSM). The mediating effect of systemic inflammation was formally tested. Machine learning was implemented to investigate the added value of dental visits in predicting high BP over the variables included in the Framingham Hypertension Risk Score among individuals without an established diagnosis of hypertension.

Results

Of 27,725 participants included in the population analysis, 46% attended a dental visit ≤6 months. In the PSM cohort (n = 2350), last dental visit attendance >6 months was consistently associated with 2 mmHg higher systolic BP (P = 0.001) and with 23 to 35% higher odds of high/uncontrolled BP compared with attendance ≤6 months. Inflammation mildly mediated the association. Access to dental care improved the prediction of high BP by 2%.

Conclusions

Dental care use impacts on BP profiles independent of socioeconomic confounders, possibly through systemic inflammation. Regular dental visits may contribute to preventive medicine.

Recurrent pericarditis is less scary: the new therapeutic solutions

Pericarditis is a common inflammatory disease affecting the pericardial sac, resulting from a variety of stimuli that trigger a stereotyped immune response. Generally self-limiting, this condition can be burdened by a significant risk of acute complications and relapses, with recurrence rates affecting up to 30% of patients, especially in the case of diagnostic and therapeutic delay. Therapeutic options in recurrent forms, initially based only on the use of traditional drugs such as colchicine, non-steroidal anti-inflammatory drugs, and corticosteroids, have recently been enriched with new molecules, such as interleukin 1 blockers anakinra and rilonacept, particularly indicated in refractory forms dependent on corticosteroids. Other medically relevant therapeutic possibilities in refractory disease include azathioprine, methotrexate, and intravenous immunoglobulins. This brief review aims to summarize the treatment strategies of recurrent pericarditis in light of the most up-to-date evidence and recommendations.

Pericarditis after SARS-CoV-2 Infection: Another Pebble in the Mosaic of Long COVID?

With the emerging success of the COVID-19 vaccination programs, the incidence of acute COVID-19 will decrease. However, given the high number of people who contracted SARS-CoV-2 infection and recovered, we will be faced with a significant number of patients with persistent symptoms even months after their COVID-19 infection. In this setting, long COVID and its cardiovascular manifestations, including pericarditis, need to become a top priority for healthcare systems as a new chronic disease process. Concerning the relationship between COVID-19 and pericardial diseases, pericarditis appears to be common in the acute infection but rare in the postacute period, while small pericardial effusions may be relatively common in the postacute period of COVID-19. Here, we reported a series of 7 patients developing pericarditis after a median of 20 days from clinical and virological recovery from SARS-CoV-2 infection. We excluded specific identifiable causes of pericarditis, hence we speculate that these cases can be contextualized within the clinical spectrum of long COVID. All our patients were treated with a combination of colchicine and either ASA or NSAIDs, but four of them did not achieve a clinical response. When switched to glucocorticoids, these four patients recovered with no recurrence during drug tapering. Based on this observation and on the latency of pericarditis occurrence (a median of 20 days after a negative nasopharyngeal swab), could be suggested that post-COVID pericarditis may be linked to ongoing inflammation sustained by the persistence of viral nucleic acid without virus replication in the pericardium. Therefore, glucocorticoids may be a suitable treatment option in patients not responding or intolerant to conventional therapy and who require to counteract the pericardial inflammatory component rather than direct an acute viral injury to the pericardial tissue.

Hypertension and Periodontitis: A Joint Report by the Italian Society of Hypertension (SIIA) and the Italian Society of Periodontology and Implantology (SIdP)

An accumulating body of evidence supports an independent association between high blood pressure (BP) and periodontitis, possibly mediated by low-grade inflammation. This joint report by the Italian Society of Hypertension (SIIA) and the Italian Society of Periodontology and Implantology (SIdP) working group on Hypertension and Periodontitis (Hy-Per Group) provides a review of the evidence on this topic encompassing epidemiology, biological plausibility, relevance, magnitude, and treatment management. Consensus recommendations are provided for health professionals on how to manage BP in individuals showing signs of poor oral health. In summary, (1) large epidemiological studies highlight that individuals with periodontal diseases have increased risk for high/uncontrolled BP independent of confounders; (2) mechanistically, low-grade inflammation might have a causal role in the association; (3) BP profile and control might benefit from periodontal treatment in pre-hypertensive and hypertensive individuals; (4) oral health status should be evaluated as a potential risk factor for high/uncontrolled BP, and effective oral care should be included as an adjunct lifestyle measure during hypertension management. Further research is needed to optimize BP management in individuals with poor oral health.

Real-world Antihypertensive Treatment Patterns, Treatment Adherence, and Blood Pressure Control in the Elderly: An Italian Awareness-raising Campaign on Hypertension by Senior Italia FederAnziani, the Italian Society of Hypertension and the Italian Federation of General Practitioners

INTRODUCTION

Achieving hypertension control is beneficial regardless of age. Fixed-combination pills have the potential of increasing adherence to treatment, improving the benefit/risk ratio, and simplifying therapy, with resulting convenience especially in the elderly.

AIM

We examined real-world antihypertensive treatment adherence and hypertension control rates in a cohort of Italian elderly individuals, enrolled in a prospective, pragmatic awareness-raising campaign on blood pressure (BP).

METHODS

13196 treated hypertensive elderly (mean age 73.2±7.5 years, 55.5% women) were recruited through opportunistic sampling, answered a brief questionnaire on antihypertensive therapy, and were followed-up for 6 months, when BP was measured as per routine care. Controlled hypertension was defined as BP < 140/90 mmHg. Real-world treatment adherence and hypertension control rates were evaluated at 6 months according to different treatment patterns (fixed-dose versus free combinations), using Yates correction for continuity to assess likelihood estimates for differences between treatments.

RESULTS

10551 participants (80%) were on a single-pill therapy and 3445 were on a fixed combination therapy of two (24.8%) or three (1.3%) drugs. Individuals on a fixed combination therapy were more adherent to treatment than the counterparts (p < 0.001). Full adherence increased with the number of drugs/pill among single-pill users (47.5%, 68.5%, and 100% with 1, 2, or 3 drugs/pill; p < 0.001). Hypertension control rates were 70% and 65.2% (p = 0.001) according to fixed or free combinations of two drugs and 71% and 63.9% (p = 0.321) for fixed or free combinations of three drugs.

CONCLUSIONS

Real-world data suggest that simplified treatment strategies and use of fixed combinations improve adherence to antihypertensive therapy and BP control in the elderly.

Real-World Hypertension Prevalence, Awareness, Treatment, and Control in Adult Diabetic Individuals: An Italian Nationwide Epidemiological Survey

Introduction

Hypertesion is the leading cause of morbidity and mortality, worldwide, and its prevalence has been increasing in several countries, including Italy.

Aims

To assess hypertension prevalence, awareness, treatment, and control in a real-world sample of adults with self-reported diabetes compared with nondiabetic individuals.

Methods

Following the 2018 World Hypertension Day, a nationwide, cross-sectional epidemiological survey on cardiovascular risk factors (“Abbasso la Pressione!”) in 3956 Italian pharmacies enrolled 47217 self-presenting volunteers (≥ 18 years). Participants underwent standardized blood pressure (BP) measurements and answered a questionnaire on cardiovascular risk factors and lifestyle habits. Questions included if they had an established diagnosis of diabetes, hypertension or were on a BP medication. Hypertension prevalence was defined as systolic BP ≥ 140 and/or diastolic BP ≥ 90 mmHg. A double definition for hypertension control based on the recent European and US guidelines on hypertension was applied.

Results

Diabetic individuals (N = 5695, 12%) had higher rates of hypertension prevalence (80% vs. 54.7%, p < 0.001), awareness (85.6% vs 77.3%, p < 0.001) and treatment (85.8% vs. 76.7%, p < 0.001), but lower hypertension control rates (36.1% vs. 39.6% according to the 2018 European guidelines, p < 0.001; 25.4% vs 30.8% according to the 2017 US guidelines, p < 0.001) than nondiabetics. Diabetic participants tended to be older, sedentary, overweight/obese, dyslipidemic men, with higher 10-years cardiovascular risk than nondiabetics (p < 0.001). Uncontrolled hypertension was associated with male gender, diabetes, body mass index, unhealthy lifestyle habits, and older age.

Conclusions

Elevated hypertension awareness and treatment rates in diabetic adults do not translate into adequate BP control in the real world. Concomitant unfavorable metabolic features and unhealthy lifestyle habits might contribute to this observation.

The Urrah study

Uric acid has long been considered responsible for a single specific disease, namely gout. In recent years, novel knowledge has emerged linking serum uric acid with a variety of conditions and related risk factors, from hypertension, metabolic syndrome, and type 2 diabetes, to fatal/nonfatal cardiovascular diseases and all-cause death, with the underlying mechanisms involving disrupted neurohormonal and metabolic signaling as well as oxidative stress and inflammation. Importantly, the cut-off value of serum uric acid predicting the risk of incident events is within the range of normality and below the threshold for increased risk of gout. A large contribution to the advancement in knowledge in the cardiovascular implications of uric acid derives from the Italian study URic acid Right for heArt Health (URRAH). This review summarizes the mechanisms linking uric acid with cardiovascular risk and the major findings of the URRAH study. The need for a reappraisal of the definition of range of normality for uric acid is discussed.

Non-pharmacological Strategies Against Systemic Inflammation: Molecular Basis and Clinical Evidence

Systemic inflammation is a common denominator to a variety of cardiovascular (CV) and non-CV diseases and relative risk factors, including hypertension and its control, metabolic diseases, rheumatic disorders, and those affecting the gastrointestinal tract. Besides medications, a non-pharmacological approach encompassing lifestyle changes and other complementary measures is mentioned in several updated guidelines on the management of these conditions. We performed an updated narrative review on the mechanisms behind the systemic impact of inflammation and the role of non-pharmacological, complementary measures centered on lowering systemic phlogosis for preserving or restoring a good global health. The central role of genetics in shaping the immune response is discussed in conjunction with that of the microbiome, highlighting the interdependence and mutual influences between the human genome and microbial integrity, diversity, and functions. Several plausible strategies to modulate inflammation and restore balanced crosstalk between the human genome and the microbiome are then recapitulated, including dietary measures, active lifestyle, and other potential approaches to manipulate the resident microbial community. To date, evidence from high-quality human studies is sparse to allow the unconditioned inclusion of understudied, though plausible solutions against inflammation into public health strategies for global wellness. This gap claims further focused, well-designed research targeted at unravelling the mechanisms behind future personalized medicine.

COVID-19 and cardiovascular diseases

Infection by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is responsible for the second pandemic of the XXI century after influenza A in 2009. As of mid-June 2020, more than 4,40,000 fatal cases of SARS-CoV-2-related disease (COVID-19) have occurred worldwide. Besides its prominent expression at the level of the respiratory apparatus, COVID-19 is also characterized by a substantial degree of cardiovascular involvement, both in terms of deterioration of pre-existing conditions, and as the effect of inflammation-facilitated acute events. They include ischemic/inflammatory heart disease, ventricular arrhythmias, conduction disturbances, thrombotic events at the level of the lungs, and systemic activation of the coagulation cascade, configuring the scenario of disseminated intravascular coagulation. Herein, we summarize the main COVID-19 features of relevance for the clinicians in the cardiovascular field. The rationale, concerns, and possible side effects of specific therapeutic measures, including anticoagulants, renin-angiotensin-aldosterone system inhibitors, and anti-inflammatory/antiviral medications applied to the treatment of COVID-19 are also discussed.

The role of Immunity in Fabry Disease and Hypertension: A Review of a Novel Common Pathway

Fabry disease is a progressive, X-linked inherited lysosomal storage disorder where accumulation of glycosphingolipids increases the risk for early cardiovascular complications, including heart failure, stroke, and end stage renal disease. Besides disease-specific therapy, blood pressure (BP) control is of central importance in Fabry disease to reduce disease progression and improve prognosis. Both Fabry disease and hypertension are characterized by the activation of the innate component of the immune system, with Toll-like receptor 4 (TLR4) as a common trigger to the inflammatory cascade. The renin-angiotensin system (RAS) participates in the establishment of low-grade chronic inflammation and redox unbalance that contribute to organ damage in the long term. Besides exploiting the anti-inflammatory effects of RAS blockade and enzyme replacement therapy, targeted therapies acting on the immune system represent an appealing field of research in these conditions. The aim of this narrative review is to examine the issue of hypertension in the setting of Fabry disease, focusing on the possible determinants of their reciprocal relationship, as well as on the related clinical and therapeutic implications.

Active gingival inflammation is linked to hypertension

BACKGROUND

Cardiovascular diseases (CVD) including hypertension, are characterized by underlying systemic inflammation. Periodontitis, which can impact the systemic inflammatory burden has recently been linked to high blood pressure (BP). However, the relationship of gingival bleeding, as an easily accessible marker of periodontal disorder, with hypertension, remains unclear.

METHODS

Survey-based propensity score matching (PSM) incorporating major confounders shared between hypertension and periodontal diseases was applied to cross-sectional NHANES III data from 5396 adults at least 30 years old who underwent BP measurement and periodontal examination, identifying two matched groups with and without gingival bleeding. The association of bleeding gums with SBP (mmHg) and high/uncontrolled BP was then assessed with generalized additive models incorporating inflammatory markers. Stratification by periodontal status (healthy; gingivitis; stable periodontitis; unstable periodontitis) was performed. Variables importance was estimated using machine learning.

RESULTS

Gingival bleeding (gingivitis; unstable periodontitis) was independently associated with +2.6 mmHg (P < 0.001) SBP compared with no bleeding (healthy periodontium; stable periodontitis), and with greater odds (OR = 1.42; 95% CI = 1.19-1.68; P < 0.001) of high/uncontrolled BP. Participants with unstable periodontitis had higher SBP than those with stable periodontitis (+2.1 mmHg; P < 0.001) or gingivitis (+5.3 mmHg; P < 0.001). Unstable periodontitis and gingivitis were consistently associated with increased risk of high/uncontrolled BP (OR = 1.65, 95% CI = 2.14-1.82; OR = 1.49, 95% CI = 1.22-1.82, respectively). Inflammatory markers allowed a maximum of 12% gain in the models' predictive power.

CONCLUSION

Gingival bleeding contributes to shaping the relationship between periodontal diseases and BP, but the burden represented by periodontitis is also crucial. Periodontal evaluation might be of importance in difficult to control hypertension.

Increased cardiovascular death rates in a COVID-19 low prevalence area

The province of L'Aquila (Central Italy) was marginally affected by COVID‐19 pandemic, but changes in health care seeking behaviors were noticed. The authors retrospectively analyzed de‐identified data concerning all‐cause and cardiovascular hospitalizations, cardiovascular acute phase treatments, and in‐hospital cardiovascular deaths in the province of L'Aquila from January 1 to March 31, in 2020 and 2019. Incidence rate ratios (IRR) comparing 2020 and 2019 for admissions/procedures were calculated through Poisson regression. All‐cause and cardiovascular mortality in the examined time windows was also assessed. Less all‐cause (IRR 0.85, P < .001) and cardiovascular (IRR 0.73, P < .001) hospitalizations occurred in 2020 than in 2019. Less daily cardiovascular procedures were also performed (IRR: 0.74, P = .009). A disproportionate decrease in the number of procedures was observed in relation to cardiovascular hospitalizations in 2020 (−5.5%, P = .001). Unlike all‐cause mortality, more in‐hospital cardiovascular deaths occurred in March 2020 compared with March 2019 (+6.8%, P = .048).

Laparoscopic Liver Resection: A South American Experience with 2887 Cases

BACKGROUND

Laparoscopic liver resections (LLR) have been increasingly performed in recent years. Most of the available evidence, however, comes from specialized centers in Asia, Europe and USA. Data from South America are limited and based on single-center experiences. To date, no multicenter studies evaluated the results of LLR in South America. The aim of this study was to evaluate the experience and results with LLR in South American centers.

METHODS

From February to November 2019, a survey about LLR was conducted in 61 hepatobiliary centers in South America, composed by 20 questions concerning demographic characteristics, surgical data, and perioperative results.

RESULTS

Fifty-one (83.6%) centers from seven different countries answered the survey. A total of 2887 LLR were performed, as follows: Argentina (928), Brazil (1326), Chile (322), Colombia (210), Paraguay (9), Peru (75), and Uruguay (8). The first program began in 1997; however, the majority (60.7%) started after 2010. The percentage of LLR over open resections was 28.4% (4.4-84%). Of the total, 76.5% were minor hepatectomies and 23.5% major, including 266 right hepatectomies and 343 left hepatectomies. The conversion rate was 9.7%, overall morbidity 13%, and mortality 0.7%.

CONCLUSIONS

This is the largest study assessing the dissemination and results of LLR in South America. It showed an increasing number of centers performing LLR with the promising perioperative results, aligned with other worldwide excellence centers.

Anti-Inflammatory and Anti-Nociceptive Effects of Cocoa: A Review on Future Perspectives in Treatment of Pain

Cocoa has been reported to have medicinal properties. It contains a wide range of phytochemicals, including polyphenols, which have been shown to exert anti-inflammatory and antioxidant actions, and also to have a positive effect on pain. Other components of cocoa might be able to positively influence pain perception through various mechanisms. Despite encouraging results from preclinical studies, there is a lack of evidence of antinociceptive effects of cocoa from clinical trials in humans. Further research is needed to better identify the active principles in cocoa, to understand the underlying mechanisms of action, and to establish efficacy in humans.

The 2020 Italian Society of Arterial Hypertension (SIIA) practical guidelines for the management of primary aldosteronism

Background and aim

Considering the amount of novel knowledge generated in the last five years, a team of experienced hypertensionlogists was assembled to furnish updated clinical practice guidelines for the management of primary aldosteronism.

Methods

To identify the most relevant studies, the authors utilized a systematic literature review in international databases by applying the PICO strategy, and then they were required to make use of only those meeting predefined quality criteria. For studies of diagnostic tests, only those that fulfilled the Standards for Reporting of Diagnostic Accuracy recommendations were considered.

Results

Each section was jointly prepared by at least two co-authors, who provided Class of Recommendation and Level of Evidence following the American Heart Association methodology. The guidelines were sponsored by the Italian Society of Arterial Hypertension and underwent two rounds of revision, eventually reexamined by an External Committee. They were presented and thoroughly discussed in two face-to-face meetings with all co-authors and then presented on occasion of the 36th Italian Society of Arterial Hypertension meeting in order to gather further feedbacks by all members. The text amended according to these feedbacks was subjected to a further peer review.

Conclusions

After this process, substantial updated information was generated, which could simplify the diagnosis of primary aldosteronism and assist practicing physicians in optimizing treatment and follow-up of patients with one of the most common curable causes of arterial hypertension.

Is there a connection among atrial fibrillation, anticoagulant treatment, and dementia?

It is well-known that atrial fibrillation carries an increased risk of stroke and dementia. The connecting pathogenic common mechanism is the thromboembolic state provided by atrial fibrillation, which is responsible for the acute cerebral events, as well as more saddle anatomic lesions, which accumulating over time, could lead to a progressive cognitive decline. It is plausible, instinctively, that oral anticoagulation could decrease this risk, although the possibility of micro-haemorrhages, which cannot be ignored, could make anticoagulation in this contest even dangerous. In this regard, whether there are firm, well established, evidences documenting a significant reduction in stroke occurrence with anticoagulant treatment in atrial fibrillation, the same level of evidences are not supporting the treatment in preventing dementia. Bringing some more clarity to this issue could have some considerable advantages, also in term of healthcare cost containment, considering the high prevalence of atrial fibrillation and dementia in the elderly.

Association between periodontal inflammation and hypertension using periodontal inflamed surface area and bleeding on probing

AIM

Periodontitis is a relapsing-remitting disease. Compared with bleeding on probing (BoP), expression of disease activity, periodontal inflamed surface area (PISA), incorporates chronic disease parameters. We tested the association of PISA and BoP with blood pressure (BP) in NHANES III.

MATERIALS AND METHODS

A total of 8,614 subjects (≥30 years) with complete periodontal and BP examinations were enrolled. PISA was derived from periodontal probing depth and BoP. The association of PISA and BoP with high/uncontrolled BP was examined by multiple-adjusted models. Inflammatory markers were tested as possible mediators. A machine learning (ML) approach was used to define the relative importance of PISA and BoP and estimate the power of BP status prediction.

RESULTS

Compared to no inflammation, severe PISA and BoP were associated with 43% (p < .001) and 32% (p = .006) higher odds of high/uncontrolled BP (≥130/80 mmHg), and with higher systolic BP by ≈4 (p < .001) and 5 (p < .001) mmHg, respectively. Inflammatory markers appeared to mediate this association with various extents, without threshold effect. BoP predicted high/uncontrolled BP more efficiently than PISA using ML.

CONCLUSION

PISA and BoP describe the association of periodontal inflammation and hypertension with subtle differences. The contribution of local inflammation to the global inflammatory burden might explain the observed findings.

Low Density Lipoprotein (LDL) Cholesterol as a Causal Role for Atherosclerotic Disease: Potential Role of PCSK9 Inhibitors

Proprotein convertase subtilisin/kexin type 9 (PCSK9)-related discoveries of the turn of the century have translated into substantial novelty in dyslipidemia treatment in the last 5 years. With chronic preventable atherosclerotic cardiovascular diseases (ASCVD) representing an epidemic of morbidity and mortality worldwide, low-density lipoprotein cholesterol (LDL-c) reduction represents a public health priority. By overcoming two major statin-related issues, namely intolerance and ineffectiveness, PCSK9 inhibitors have offered a safe and effective option in selected clinical settings where LDL-c reduction is required. Herein, we recapitulate recent findings, clinical applications, and ASCVD prevention potential of PCSK9 inhibition, with focus on anti-PCSK9 monoclonal antibodies, evolocumab and alirocumab.

Hypertension Management at Older Age: An Update

Hypertension is a risk factor for cardiovascular morbidity and mortality with increasing prevalence with age, whose treatment is associated with benefits over fatal and non-fatal cardiovascular events even later in life. However, there are persistent concerns on the short- and long-term weighted benefits of treating hypertension in the very old, particularly in those with specific clinical features. In fact, a broad range of clinical scenarios can be observed at older ages, spanning from the healthy to the frailest patient, and hypertension clinical trials have traditionally excluded the latter, thus preventing the unconditioned application to these patients of the same recommendations as in younger ages. Persistent issues regarding high blood pressure management in the very old adult are mainly related to treatment threshold and targets, which have been differently addressed by American and European guidelines. Herein, we will examine the challenges related to high blood pressure treatment in healthy and frail older and very old adults. We will discuss the evidence behind current recommendations. Finally, we will recapitulate the recommended treatment options for high blood pressure in these patients in the light of the most recent guidelines.

Diastolic blood pressure and risk profile in renal and cardiovascular diseases. Results from the SPRINT trial

The Systolic Blood Pressure Intervention Trial (SPRINT) trial demonstrated the efficacy and safety of targeting a systolic blood pressure of <120 mmHg compared to <140 mmHg in selected hypertensive patients. Some evidence, however, suggests a J-curve for; diastolic blood pressure (DBP) particularly in subjects with cardiovascular (CV) and chronic kidney disease. We evaluated the risk of events in SPRINT with focus on these subgroups according to DBP. Mean DBP (±standard deviation) throughout follow-up time was calculated for each patient. Patients were then categorized into five groups according to mean DBP (<60 mmHg, 60-69 mmHg, 70-79 mmHg [reference], 80-89 mmHg, ≥90 mmHg); hazard ratio for outcomes was assessed overall and in the predefined subgroups. A higher risk for CV events was observed in the lower DBP range overall (hazard ratio 1.46, confidential interval 95% 1.1-1.95, P < .001), but not in the absence of pre-existing CV or renal disease. Indeed, such risk significantly increased above 80 mmHg in patients with CV disease and below 70 mmHg in those with chronic kidney disease for selected outcomes. DBP<70 mmHg particularly affected renal outcomes irrespective of renal status. Different risk profiles according to DBP appear to be related to specific clinical characteristics in SPRINT. These findings require further testing in dedicated trials with appropriate follow-up.

Orthostatic changes in systolic blood pressure among SPRINT participants at baseline

Orthostatic changes in systolic blood pressure (SBP) impact cardiovascular outcomes. In this study, we aimed to determine the pattern of orthostatic systolic pressure changes in participants enrolled in the SBP Intervention Trial (SPRINT) at their baseline visit before randomization and sought to understand clinical factors predictive of these changes. Of the 9323 participants enrolled in SPRINT, 8662 had complete data for these analyses. The SBP after 1 minute of standing was subtracted from the mean value of the three preceding seated SBP values. At the baseline visit, medical history, medications, anthropometric measures, and standard laboratory testing were undertaken. The mean age of SPRINT participants was 68 years, two-thirds were male, with 30% black, 11% Hispanic, and 55% Caucasian. The spectrum of SBP changes on standing demonstrated that increases in SBP were as common as declines, and about 5% of participants had an increase, and 5% had a decrease of >20 mm Hg in SBP upon standing. Female sex, taller height, more advanced kidney disease, current smoking, and several drug classes were associated with larger declines in BP upon standing, while black race, higher blood levels of glucose and sodium, and heavier weight were associated with more positive values of the change in BP upon standing. Our cross-sectional results show a significant spectrum of orthostatic SBP changes, reflecting known (eg, age) and less well-known (eg, kidney function) relationships that may be important considerations in determining the optimal target blood pressure in long-term outcomes of older hypertensive patients.

Occurrence of spontaneous periodontal disease in the SAMP1/YitFc murine model of Crohn disease

BACKGROUND

Oral involvement is often associated with inflammatory bowel disease (IBD). Recent evidence suggests a high incidence of periodontal disease in patients with Crohn disease (CD). To the best of the authors' knowledge, no animal model of IBD that displays associated periodontal disease was reported previously. The aim of this study is to investigate the occurrence and progression of periodontal disease in SAMP1/YitFc (SAMP) mice that spontaneously develop a CD-like ileitis. In addition, the temporal correlation between the onset and progression of periodontal disease and the onset of ileitis in SAMP mice was studied.

METHODS

At different time points, SAMP and parental AKR/J (AKR) control mice were sacrificed, and mandibles were prepared for stereomicroscopy and histology. Terminal ilea were collected for histologic assessment of inflammation score. Periodontal status, i.e., alveolar bone loss (ABL) and alveolar bone crest, was examined by stereomicroscopy and histomorphometry, respectively.

RESULTS

ABL increased in both strains with age. SAMP mice showed greater ABL compared with AKR mice by 12 weeks of age, with maximal differences observed at 27 weeks of age. AKR control mice did not show the same severity of periodontal disease. Interestingly, a strong positive correlation was found between ileitis severity and ABL in SAMP mice, independent of age.

CONCLUSIONS

The present results demonstrate the occurrence of periodontal disease in a mouse model of progressive CD-like ileitis. In addition, the severity of periodontitis strongly correlated with the severity of ileitis, independent of age, suggesting that common pathogenic mechanisms, such as abnormal immune response and dysbiosis, may be shared between these two phenotypes.

Chronic hyperuricemia, uric acid deposit and cardiovascular risk

Hyperuricemia is commonly associated with traditional risk factors such as dysglicemia, dyslipidemia, central obesity and abnormal blood pressure, i.e. the metabolic syndrome. Concordantly, recent studies have revived the controversy over the role of circulating uric acid, hyperuricemia, and gout as an independent prognostic factor for cardiovascular morbidity and mortality. In this regard, different studies also evaluated the possible role of xanthine inhibitors in inducing blood pressure reduction, increment in flow-mediated dilation, and improved cardiovascular prognosis in various patient settings. The vast majority of these studies have been conducted with either allopurinol or its active metabolite oxypurinol, i.e. two purine-like non-selective inhibitors of xanthine oxidase. More recently, the role of uric acid as a risk factor for cardiovascular disease and the possible protective role exerted by reduction of hyperuricemia to normal level have been evaluated by the use of febuxostat, a selective, non purine-like xanthine oxidase inhibitor. In this review, we will report current evidence on hyperuricemia in cardiovascular disease. The value of uric acid as a biomarker and as a potential therapeutic target for tailored old and novel "cardiometabolic" treatments will be also discussed.

Reliability and precision of neural spike timing: simulation of spectrally broadband synaptic inputs

Spectrally broadband stimulation of neurons has been an effective method for studying their dynamic responses to simulated synaptic inputs. Previous studies with such stimulation were mostly based upon the direct intracellular injection of noisy current waveforms. In the present study we analyze and compare the firing output of various identified molluscan neurons to aperiodic, broadband current signals using three types of stimulus paradigms: 1. direct injection in current clamp mode, 2. conductance injection using electrotonic coupling of the input waveform to the neuron, and 3. conductance injection using a simulated chemical excitatory connection. The current waveforms were presented in 15 successive trials and the trial-to-trial variations of the spike responses were analyzed using peri-stimulus spike density functions. Comparing the responses of the neurons to the same type of input waveforms, we found that conductance injection resulted in more reliable and precise spike responses than direct current injection. The statistical parameters of the response spike trains depended on the spectral distribution of the input. The reliability increased with increasing cutoff frequency, while the temporal jitter of spikes changed in the opposite direction. Neurons with endogenous bursting displayed lower reproducibility in their responses to noisy waveforms when injected directly; however, they fired far more reliably and precisely when receiving the same waveforms as conductance inputs. The results show that molluscan neurons are capable of accurately reproducing their responses to synaptic inputs. Conductance injection provides an enhanced experimental technique for assessing the neurons' spike timing reliability and it should be preferred over direct current injection of noisy waveforms.

Recovery of hidden information through synaptic dynamics

The role of synaptic dynamics in processing neural information is investigated in a neural information channel with realistic model neurons having chaotic intrinsic dynamics. Our neuron models are realized in simple analogue circuits, and our synaptic connections are realized both in analogue circuits and through a dynamic clamp program. The information which is input to the first chaotic neuron in the channel emerges partially absent and partially 'hidden'. Part is absent because of the dynamical effects of the chaotic oscillation that effectively acts as a noisy channel. The 'hidden' part is recoverable. We show that synaptic parameters, most significantly receptor binding time constants, can be tuned to enhance the information transmission by the combination of a neuron plus a synapse. We discuss how the dynamics of the synapse can be used to recover 'hidden' information using average mutual information as a measure of the quality of information transport.

Extended dynamic clamp: controlling up to four neurons using a single desktop computer and interface

The dynamic clamp protocol allows an experimenter to simulate the presence of membrane conductances in, and synaptic connections between, biological neurons. Existing protocols and commercial ADC/DAC boards provide ready control in and between < or =2 neurons. Control at >2 sites is desirable when studying neural circuits with serial or ring connectivity. Here, we describe how to extend dynamic clamp control to four neurons and their associated synaptic interactions, using a single IBM-compatible PC, an ADC/DAC interface with two analog outputs, and an additional demultiplexing circuit. A specific C++ program, DYNCLAMP4, implements these procedures in a Windows environment, allowing one to change parameters while the dynamic clamp is running. Computational efficiency is increased by varying the duration of the input-output cycle. The program simulates < or =8 Hodgkin-Huxley-type conductances and < or =18 (chemical and/or electrical) synapses in < or =4 neurons and runs at a minimum update rate of 5 kHz on a 450 MHz CPU. (Increased speed is possible in a two-neuron version that does not need auxiliary circuitry). Using identified neurons of the crustacean stomatogastric ganglion, we illustrate on-line parameter modification and the construction of three-member synaptic rings.

The role of liver transplantation in patients with Caroli's disease

Caroli's disease, characterized by segmental or diffuse dilation of the intrahepatic biliary ducts, is a rare disease which is difficult to treat. The course of the disorder is characterized by recurrent episodes of cholangitis and hospital stays, with a consequent loss of quality-of-life and productive capacity, often ending in death due to uncontrolled infection. Endoscopic drainage of the bile duct, percutaneously or surgically, is palliative, and presents bad results in the follow-up of these patients. Orthotopic liver transplantation appears to be an effective curative option for the treatment of patients with Caroli's disease associated to complications. The authors present the course of two cases of this disease, associated with congenital fibrosis of the liver worsened by repeated episodes of cholangitis, submitted to orthotopic liver transplantation.

A comparison between topical and infiltrative bupivacaine and intravenous meperidine for postoperative analgesia after inguinal herniorrhaphy

The purpose of the present study is to compare postoperative analgesia offered by the simple instillation of local anesthetic on the surgical wound, its infiltration with the same local anesthetic, and the use of an intravenous opioid. Sixty patients were divided into the three analgesia groups to be studied: instillation of local anesthetic (Group I), injection of local anesthetic (Group II), and intravenous opioid (Group III). The pain was quantified using the visual analogue scale. It was observed that there was better analgesia in Groups I and II during the first 6 hours postoperatively as compared with Group III (P < 0.0001). At the end of the 12 hours the three modes of analgesia proved comparable. However, after 24 hours there was better analgesic development in Group I, whereas Group II had greater postoperative morbidity. We conclude that the instillation of local anesthesia provides analgesia during the immediate postoperative period comparable to local infiltration using the same anesthetic. Both regional analgesia methods are more effective analgesics during the first 6 hours than are intravenous opioids. Furthermore the simple instillation of local anesthetic allows better analgesic evolution of the surgical wound after the first 24 hours considering the lower rate of resulting complications.

Reliable circuits from irregular neurons: a dynamical approach to understanding central pattern generators

Central pattern generating neurons from the lobster stomatogastric ganglion were analyzed using new nonlinear methods. The LP neuron was found to have only four or five degrees of freedom in the isolated condition and displayed chaotic behavior. We show that this chaotic behavior could be regularized by periodic pulses of negative current injected into the neuron or by coupling it to another neuron via inhibitory connections. We used both a modified Hindmarsh-Rose model to simulate the neurons behavior phenomenologically and a more realistic conductance-based model so that the modeling could be linked to the experimental observations. Both models were able to capture the dynamics of the neuron behavior better than previous models. We used the Hindmarsh-Rose model as the basis for building electronic neurons which could then be integrated into the biological circuitry. Such neurons were able to rescue patterns which had been disabled by removing key biological neurons from the circuit.

Synchronous behavior of two coupled electronic neurons

We report on experimental studies of synchronization phenomena in a pair of analog electronic neurons (ENs). The ENs were designed to reproduce the observed membrane voltage oscillations of isolated biological neurons from the stomatogastric ganglion of the California spiny lobster Panulirus interruptus. The ENs are simple analog circuits which integrate four-dimensional differential equations representing fast and slow subcellular mechanisms that produce the characteristic regular/chaotic spiking-bursting behavior of these cells. In this paper we study their dynamical behavior as we couple them in the same configurations as we have done for their counterpart biological neurons. The interconnections we use for these neural oscillators are both direct electrical connections and excitatory and inhibitory chemical connections: each realized by analog circuitry and suggested by biological examples. We provide here quantitative evidence that the ENs and the biological neurons behave similarly when coupled in the same manner. They each display well defined bifurcations in their mutual synchronization and regularization. We report briefly on an experiment on coupled biological neurons and four-dimensional ENs, which provides further ground for testing the validity of our numerical and electronic models of individual neural behavior. Our experiments as a whole present interesting new examples of regularization and synchronization in coupled nonlinear oscillators.

Homoclinic tangency and chaotic attractor disappearance in a dripping faucet experiment

A sequence of attractors, reconstructed from interdrops time series data of a leaky faucet experiment, is analyzed as a function of the mean dripping rate. We established the presence of a saddle point and its manifolds in the attractors and we explained the dynamical changes in the system using the evolution of the manifolds of the saddle point, as suggested by the orbits traced in first return maps. The sequence starts at a fixed point and evolves to an invariant torus of increasing diameter (a Hopf bifurcation) that pushes the unstable manifold towards the stable one. The torus breaks up and the system shows a chaotic attractor bounded by the unstable manifold of the saddle. With the attractor expansion the unstable manifold becomes tangential to the stable one, giving rise to the sudden disappearance of the chaotic attractor, which is an experimental observation of a so called chaotic blue sky catastrophe.