Dynamics of beating cardiac tissue under slow periodic drives

Effects of mechanical coupling on cardiac dynamics are studied by monitoring the beating dynamics of a cardiac tissue which is being pulled periodically at a pace slower than its intrinsic beating rate. The tissue is taken from the heart of a bullfrog that includes pacemaker cells. The cardiac tissue beats spontaneously with an almost constant interbeat interval (IBI) when there is no external forcing. On the other hand, the IBI is observed to vary significantly under an external periodic drive. Interestingly, when the period of the external drive is about two times the intrinsic IBI of the tissue without pulling, the IBI as a function of time exhibits a wave packet structure. Our experimental results can be understood theoretically by a phase-coupled model under external driving. In particular, the theoretical prediction of the wave-packet period as a function of the normalized driving period agrees excellently with the observations. Furthermore, the cardiac mechanical coupling constant can be extracted from the experimental data from our model and is found to be insensitive to the external driving period. Implications of our results on cardiac physiology are also discussed.

Respiratory Syncytial Virus Infection of Human Lung Fibroblasts Induces a Hyaluronan-Enriched Extracellular Matrix That Binds Mast Cells and Enhances Expression of Mast Cell Proteases

Human lung fibroblasts (HLFs) treated with the viral mimetic polyinosine-polycytidylic acid (poly I:C) form an extracellular matrix (ECM) enriched in hyaluronan (HA) that avidly binds monocytes and lymphocytes. Mast cells are important innate immune cells in both asthma and acute respiratory infections including respiratory syncytial virus (RSV); however, the effect of RSV on HA dependent mast cell adhesion and/or function is unknown. To determine if RSV infection of HLFs leads to the formation of a HA-enriched ECM that binds and enhances mast cell activity primary HLFs were infected with RSV for 48 h prior to leukocyte binding studies using a fluorescently labeled human mast cell line (LUVA). Parallel HLFs were harvested for characterization of HA production by ELISA and size exclusion chromatography. In separate experiments, HLFs were infected as above for 48 h prior to adding LUVA cells to HLF wells. Co-cultures were incubated for 48 h at which point media and cell pellets were collected for analysis. The role of the hyaladherin tumor necrosis factor-stimulated gene 6 (TSG-6) was also assessed using siRNA knockdown. RSV infection of primary HLFs for 48 h enhanced HA-dependent LUVA binding assessed by quantitative fluorescent microscopy. This coincided with increased HLF HA synthase (HAS) 2 and HAS3 expression and decreased hyaluronidase (HYAL) 2 expression leading to increased HA accumulation in the HLF cell layer and the presence of larger HA fragments. Separately, LUVAs co-cultured with RSV-infected HLFs for 48 h displayed enhanced production of the mast cell proteases, chymase, and tryptase. Pre-treatment with the HA inhibitor 4-methylumbelliferone (4-MU) and neutralizing antibodies to CD44 (HA receptor) decreased mast cell protease expression in co-cultured LUVAs implicating a direct role for HA. TSG-6 expression was increased over the 48-h infection. Inhibition of HLF TSG-6 expression by siRNA knockdown led to decreased LUVA binding suggesting an important role for this hyaladherin for LUVA adhesion in the setting of RSV infection. In summary, RSV infection of HLFs contributes to inflammation via HA-dependent mechanisms that enhance mast cell binding as well as mast cell protease expression via direct interactions with the ECM.

Elevated plasma and synovial fluid interleukin-8 and interleukin-18 may be associated with the pathogenesis of knee osteoarthritis

PURPOSE

Osteoarthritis (OA) of the knee is a multifactorial degenerative disease typically defined as the 'wear and tear' of articular joint cartilage. However, recent studies suggest that OA is a disease arising from chronic low-grade inflammation. We conducted a study to investigate the relationship between chronic inflammatory mediators present in both the systemic peripheral blood system and localised inflammation in synovial fluid (SF) of OA and non-OA knees; and subsequently made direct comparative analyses to understand the mechanisms that may underpin the processes involved in OA.

METHODS

20-Plex proteins were quantified using Human Magnetic Luminex® assay (R&D Systems, USA) from plasma and SF of OA (n = 14) and non-OA (n = 14) patients. Ingenuity Pathway Analysis (IPA) software was used to predict the relationship and possible interaction of molecules pertaining to OA.

RESULTS

There were significant differences in plasma level for matrix metalloproteinase (MMP)-3, interleukin (IL)-27, IL-8, IL-4, tumour necrosis factor-alpha, MMP-1, IL-15, IL-21, IL-10, and IL-1 beta between the groups, as well as significant differences in SF level for IL-15, IL-8, vascular endothelial growth factor (VEGF), MMP-1, and IL-18. Our predictive OA model demonstrated that toll-like receptor (TLR) 2, macrophage migration inhibitory factor (MIF), TLR4 and IL-1 were the main regulators of IL-1B, IL-4, IL-8, IL-10, IL-15, IL-21, IL-27, MMP-1 and MMP-3 in the plasma system; whilst IL-1B, TLR4, IL-1, and basigin (BSG) were the regulators of IL-4, IL-8, IL-10, IL-15, IL-18, IL-21, IL-27, MMP-1, and MMP-3 in the SF system.

CONCLUSION

The elevated plasma IL-8 and SF IL-18 may be associated with the pathogenesis of OA via the activation of MMP-3.

The impact of participation in support groups on mental health of parents having children with autism

Introduction

Whilst there is accumulated evidence about the high prevalence of stress and mood disorders in parents of children with autism, few studies have shown that participating in parental support groups was associated with less mental health problems. This study was aimed to explore the association of participation in support groups with stress and mood disorders in parents of children with autism in Kazakhstan.

Methods

Participants (n = 146) were recruited to this cross-sectional survey from autism non-governmental organizations and Republican Children’s Rehabilitation Center in Nur-Sultan city during April-December 2018. A 59 item survey consisted of questions on parental socio-demographics, needs, participation in support groups, depression, anxiety and stress (DASS), and Multidimensional Scale of Perceived Social Support (MSPSS). Descriptive, bivariate and multivariate logistic regression analyses were performed in STATA 15.

Results

44.4% of parents reported experiencing stress, and almost half of the sample had elevated depressive (53.7%) and anxiety symptoms (47.4%). 45.3% of participants were members of parental organizations; there were no significant differences in the prevalence of stress and mood disorders among members and non-members of parental support groups. Results of the multivariate logistic regression showed that parents with older autistic children (OR 1.37, p-value 0.001), less family support (OR 0.894, p-value 0.044) and higher income (OR 3.01, p-value 0.025) were more likely to be members of support groups.

Conclusions

These findings indicate the need to increase support groups to under-served populations of Kazakhstan’s families with autistic children. Additional efforts are needed to strengthen the role of support groups in meeting the emotional needs of the parents.

Key messages

Parents of children with autism spectrum disorder experience elevated level of stress and mood disorders; however participation in support groups was not beneficial for relieving parental distress. Further research is warranted to explore the benefits of participation in support groups, and interventions are needed to strengthen the role of support groups in meeting the needs of parents.

Depression and anxiety among university students in Hong Kong

INTRODUCTION

Entry into tertiary education is a critical juncture where adolescents proceed to adulthood. This study aimed to determine the prevalence of depression and anxiety, and factors associated with such symptoms, among university undergraduate students in Hong Kong.

METHODS

A cross-sectional questionnaire study was employed. A total of 1200 undergraduate students from eight University Grants Committee-funded universities were invited to complete three sets of questionnaires, including the 9-item patient health questionnaire for screening of depressive symptoms, the 7-item generalised anxiety disorder scale for screening of anxiety symptoms, and a socio-demographic questionnaire.

RESULTS

Among the valid responses (n=1119) analysed, 767 (68.5%) respondents indicated mild to severe depressive symptoms, which were associated with mild to severe anxiety symptoms. Several lifestyle and psychosocial variables, including regular exercise, self-confidence, satisfaction with academic performance, and optimism towards the future were inversely related with mild to severe depressive symptoms. A total of 599 (54.4%) respondents indicated mild to severe anxiety symptoms, which were associated with level of academic difficulty. Satisfaction with friendship, sleep quality, and self-confidence were inversely associated with mild to severe anxiety symptoms.

CONCLUSION

More than 50% of respondents expressed some degree of depressive and anxiety symptoms (68.5% and 54.4%, respectively). Approximately 9% of respondents exhibited moderately severe to severe depressive symptoms; 5.8% exhibited severe anxiety symptoms. Respondents reporting regular exercise, higher self-confidence, and better satisfaction with both friendship and academic performance had fewer depressive and anxiety symptoms.

Risk factors associated with 1-year mortality among patients with HIV-associated tuberculosis in areas with intermediate tuberculosis burden and low HIV prevalence

INTRODUCTION

Data are limited regarding risk factors for mortality among patients with human immunodeficiency virus (HIV)-associated tuberculosis (TB) in areas with low HIV prevalence and intermediate TB burden, such as the Western Pacific region. This study aimed to assess such risk factors in Hong Kong, which has an intermediate TB burden and low HIV prevalence.

METHODS

We conducted a retrospective cohort analysis of adult patients reported to the Hong Kong TB-HIV Registry between 2006 and 2015. Baseline characteristics were compared with Kaplan-Meier estimates. Cox proportional hazards regression modelling was used to identify factors associated with mortality.

RESULTS

Of 299 patients studied, 21 (7.0%) died within 12 months of anti-TB treatment (median [interquartile range], 7.5 [3.8-10] months). The median age of death was 54 (interquartile range, 40.5-75.0) years. The cause of death was TB in five and unrelated to TB in the remaining 16. Cox proportional hazards regression showed that older age (adjusted hazard ratio=4.5; 95% confidence interval [CI]=1.4-14.9), history of drug addiction (4.6; 95% CI=1.6-13.0), and low baseline CD4 cell count of <50/μL (2.9; 95% CI=1.1-7.7) were independent risk factors for death within 12 months.

CONCLUSION

This study complements previous studies by providing information regarding risk factors associated with mortality among patients with HIV-associated TB in areas with intermediate TB burden and low HIV prevalence. The results from our study may guide targeted measures to improve survival in other areas with intermediate TB burden and low HIV prevalence, such as the Western Pacific region.

Levobupivacaine versus Racemic Bupivacaine in Spinal Anaesthesia for Urological Surgery

Racemic bupivacaine is the most common local anaesthetic used intrathecally. This prospective, randomized, double-blind study compared the clinical efficacy and motor block of 0.5% levobupivacaine with 0.5% racemic bupivacaine in spinal anaesthesia for urological surgery. The surgery required an upper level of sensory block of at least the tenth thoracic dermatome. Fifty patients were recruited (levobupivacaine group n=24; bupivacaine group n=26). Spinal anaesthesia was achieved with 2.6 ml of study solution injected in the subarachnoid space at the lumbar 3/4 interspace. One patient from the levobupivacaine group was excluded due to technical failure. There were no significant differences between the two groups in the quality of sensory and motor block or in haemodynamic change. Anaesthesia was adequate and patient satisfaction good in all cases.

We conclude that 0.5% levobupivacaine can be used as an alternative to 0.5% racemic bupivacaine in spinal anaesthesia for surgery when a sensory block to at least T10 is required.

Survey on prevalence of lower urinary tract symptoms in an Asian population

INTRODUCTION

Lower urinary tract symptoms (LUTS) have a strong effect on socio-economic and individual quality of life. The aim of the present study was to investigate the prevalence of LUTS in an Asian population.

METHODS

A telephone survey of individuals aged ≥40 years and of Chinese ethnicity was conducted. The survey included basic demographics, medical and health history, drinking habits, International Prostate Symptom Score, overactive bladder symptom score, Patient Health Questionnaire (PHQ-9) score, and Short Form (SF)-12v2 score.

RESULTS

From March to May 2017, 18 881 calls were made, of which 1543 fulfilled the inclusion criteria. In the end, 1000 successful respondents were recruited (302 men and 698 women). Age-adjusted prevalence of overactive bladder syndrome was 15.1%. The older the respondent, the more prevalent the storage symptoms and voiding symptoms (storage symptoms: r=0.434, P<0.001; voiding symptom: r=0.190, P<0.001). Presence of hypertension and diabetes were found to be significantly and positively correlated with storage and voiding symptoms. Storage and voiding symptoms were found to affect PHQ-9 scores (storage symptoms: r=0.257, P<0.001; voiding symptoms: r=0.275, P<0.001) and SF-12v2 scores (storage symptoms: r=0.467, P<0.001; voiding symptoms: r=0.335; P<0.001). Nocturia was the most prominent symptom among patients who sought medical help for their LUTS.

CONCLUSIONS

Lower urinary tract symptoms are common in Asian populations. Both storage and voiding symptoms have a negative impact on mental health and general well-being of individuals.

Increased Hyaluronan and TSG-6 in Association with Neuropathologic Changes of Alzheimer's Disease

Little is known about the extracellular matrix (ECM) during progression of AD pathology. Brain ECM is abundant in hyaluronan (HA), a non-sulfated glycosaminoglycan synthesized by HA synthases (HAS) 1-3 in a high molecular weight (MW) form that is degraded into lower MW fragments. We hypothesized that pathologic severity of AD is associated with increases in HA and HA-associated ECM molecules. To test this hypothesis, we assessed HA accumulation and size; HA synthases (HAS) 1-3; and the HA-stabilizing hyaladherin, TSG-6 in parietal cortex samples from autopsied research subjects with not AD (CERAD = 0, Braak = 0- II, n = 12-21), intermediate AD (CERAD = 2, Braak = III-IV, n = 13-18), and high AD (CERAD = 3, Braak = V-VI, n = 32-40) neuropathologic change. By histochemistry, HA was associated with deposits of amyloid and tau, and was also found diffusely in brain parenchyma, with overall HA quantity (measured by ELSA) significantly greater in brains with high AD neuropathology. Mean HA MW was similar among the samples. HAS2 and TSG-6 mRNA expression, and TSG-6 protein levels were significantly increased in high AD and both molecules were present in vasculature, NeuN-positive neurons, and Iba1-positive microglia. These results did not change when accounting for gender, advanced age (≥ 90 years versus <90 years), or the clinical diagnosis of dementia. Collectively, our results indicate a positive correlation between HA accumulation and AD neuropathology, and suggest a possible role for HA synthesis and metabolism in AD progression.

Asthmatic bronchial epithelial cells promote the establishment of a Hyaluronan-enriched, leukocyte-adhesive extracellular matrix by lung fibroblasts

Background

Airway inflammation is a hallmark of asthma. Alterations in extracellular matrix (ECM) hyaluronan (HA) content have been shown to modulate the recruitment and retention of inflammatory cells. Bronchial epithelial cells (BECs) regulate the activity of human lung fibroblasts (HLFs); however, their contribution in regulating HLF production of HA in asthma is unknown. In this study, we tested the hypothesis that BECs from asthmatic children promote the generation of a pro-inflammatory, HA-enriched ECM by HLFs, which promotes the retention of leukocytes.

Methods

BECs were obtained from well-characterized asthmatic and healthy children ages 6–18 years. HLFs were co-cultured with BECs for 96 h and samples were harvested for analysis of gene expression, synthesis and accumulation of HA, and subjected to a leukocyte adhesion assay with U937 monocytes.

Results

We observed increased expression of HA synthases HAS2 and HAS3 in HLFs co-cultured with asthmatic BECs. Furthermore, we demonstrated greater total accumulation and increased synthesis of HA by HLFs co-cultured with asthmatic BECs compared to healthy BEC/HLF co-cultures. ECM generated by HLFs co-cultured with asthmatic BECs displayed increased HA-dependent adhesion of leukocytes in a separate in vitro binding assay.

Conclusions

Our findings demonstrate that BEC regulation of HA production by HLFs is altered in asthma, which may in turn promote the establishment of a more leukocyte-permissive ECM promoting airway inflammation in this disease.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0849-1) contains supplementary material, which is available to authorized users.

Delayed diagnosis of tuberculosis: risk factors and effect on mortality among older adults in Hong Kong

OBJECTIVE

To assess the risk factors and effects of delayed diagnosis on tuberculosis (TB) mortality in Hong Kong.

METHODS

All consecutive patients with TB notified in 2010 were tracked through their clinical records for treatment outcome until 2012. All TB cases notified or confirmed after death were identified for a mortality survey on the timing and causes of death.

RESULTS

Of 5092 TB cases notified, 1061 (20.9%) died within 2 years of notification; 211 (4.1%) patients died before notification, 683 (13.4%) died within the first year, and 167 (3.3%) died within the second year after notification. Among the 211 cases with TB notified after death, only 30 were certified to have died from TB. However, 52 (24.6%) died from unspecified pneumonia/sepsis possibly related to pulmonary TB. If these cases are counted, the total TB-related deaths increases from 191 to 243. In 82 (33.7%) of these, TB was notified after death. Over 60% of cases in which TB diagnosed after death involved patients aged ≥80 years and a similar proportion had an advance care directive against resuscitation or investigation. Independent factors for TB notified after death included female sex, living in an old age home, drug abuse, malignancy other than lung cancer, sputum TB smear negative, sputum TB culture positive, and chest X-ray not done.

CONCLUSIONS

High mortality was observed among patients with TB aged ≥80 years. Increased vigilance is warranted to avoid delayed diagnosis and reduce the transmission risk, especially among elderly patients with co-morbidities living in old age homes.

Retinal Pigment Epithelial Tear after Ranibizumab Therapy for Subfoveal Fibrovascular Pigment Epithelial Detachment

Purpose

To describe the unusual complication of retinal pigment epithelial (RPE) tear after intravitreal ranibizumab (Lucentis®) for subfoveal fibrovascular pigment epithelial detachment (PED) and its effective management.

Methods

Chart review for case report of RPE tear after ranibizumab.

Results

An inferior RPE tear was documented by fluorescein angiography, fundus photography, and optical coherence tomography (OCT) 1 month after receiving repeat ranibizumab injection in the right eye of a patient with bilateral subfoveal fibrovascular PED. He had undergone multiple bevacizumab followed by ranibizumab injections for neovascular age-related macular degeneration (AMD) in both eyes, starting 6 months previously. Subsequent antivascular endothelial growth factor (VEGF) therapy improved vision of right eye from 20/200 to 20/40, despite RPE tear.

Conclusions

RPE tear may form after anti-VEGF therapy, including ranibizumab injection. Further anti-VEGF therapy may preserve or improve vision. To the authors' knowledge, this is first case report of effective suppression of neovascular activity with bevacizumab after an RPE tear following ranibizumab therapy.

A Case of Methanol Poisoning

A 29-year-old male took about 300 ml industrial alcohol in a suicidal attempt. The industrial alcohol was later confirmed to be methanol. He presented to the emergency department 10 hours post-ingestion with an anion gap metabolic acidosis and an osmol gap of 76.7 mOsm/kg. Ethanol infusion was started in the emergency department at 11 hours post-ingestion before the availability of serum methanol level. The clinical diagnosis of toxic alcohol ingestion was based on the history, arterial blood gases results and the presence of a significant osmol gap. The patient was then admitted to the intensive care unit for ethanol therapy and haemodialysis. Prompt initiation of ethanol therapy and the subsequent intensive care prevented the development of life-threatening complications of methanol poisoning in this case.

Toxicology Training Unit in Emergency Department Reduces Admission to other Specialties and Hospital Length of Stay

Objective

To evaluate the outcome of intoxicated patients presented to Accident and Emergency Department (AED) in Hong Kong with Toxicology Training Unit accreditation and AED without toxicology team.

Method

A retrospective observational study with data collection from all intoxicated cases reported through Pre-hospital Activated Charcoal Programme, a protocol driven poisoning reporting system, from 1/7/2011 to 30/6/2013 (2 years). Data on basic demographic data (e.g. sex, age), receiving AED, admission rate to other specialty, length of stay in hospital exclude psychiatry ward admission and clinical outcome were collected and analysed. Five AEDs with Toxicology Training Unit (study group) and 7 AEDs without toxicology team (control group) were included.

Results

A total of 329 intoxicated cases were included in this study. The basic epidemiological data were similar in both groups. There was a significantly lower in hospital admissions in study group (16.9%) than in control group (69.3%; p<0.001) and significant shorter median of hospital stay of 22.1 hours (interquartile range [IQR] 12.8-43.5 hours) in study group compare to 42.7 hours (IQR 20.4-76.1 hours) in control group (p<0.001).

Conclusion

Our findings show that the establishment of the toxicology training unit can achieve significant reduction in admissions to other specialty and the length of stay in hospital in the management of patients with acute intoxication.

Hot Water Immersion Therapy with a Thermal Isolator in Patient with Marine Envenomation

Objective

Hot water immersion (HWI) has been proven to be effective for the treatment of pain due to marine envenomation. Our preliminary study by simply measuring the temperature change over time on the hot water in our conventional metal tray method revealed a too rapid fall in water temperature that happened in minutes. The aim of this study was to review the current practice of HWI for patients with marine envenomation in the emergency departments in Hong Kong, and to look for the optimal equipment in performing HWI.

Method

We first conducted a phone survey to 16 registered nurses or nursing officers from 16 emergency departments of public hospitals in Hong Kong for the current practice of hot water immersion. The second part of our study was an in-vitro experiment done in observation room that a healthy subject immersed a hand into the water bath in metallic tray, sharp box and thermal isolator with and without covering of aluminum foil or plastic foil. The temperature change of the water bath in these containers was serially monitored.

Results

In our phone survey, 14 respondents used plastic tray or sharp box for hot water immersion. Nine of them claimed that they commonly encountered inadequate wound pain relief and early cooling of the hot water bath. The experiment showed that the water temperature dropped out of optimal range for 5 minutes and 15 minutes in metallic tray and sharp box respectively. The thermal isolator kept the optimal temperature throughout 30 minutes of the study time.

Conclusion

Our purposed thermal isolator is a safe, practical and effective device for HWI therapy.

Patient opinion of lower urinary tract symptoms and their treatment: a cross-sectional survey in Hong Kong public urology clinics

INTRODUCTION

Lower urinary tract symptoms collectively represent a common condition among ageing men. There are, however, limited data on the frequency of individual symptoms in patients who seek specialist care. We conducted a multinational survey in South-East Asia to evaluate patients' self-reported prevalence, bother, treatment, and treatment satisfaction of four lower urinary tract symptoms namely, urgency, nocturia, slow stream, and post-micturition dribble. This report presents the analysis of the Hong Kong subpopulation.

METHODS

This cross-sectional survey involved adult men aged over 18 years who attended a urology out-patient clinic because of lower urinary tract symptoms. A structured questionnaire, translated and validated in the local languages, was self-administered by patients.

RESULTS

Of 1436 respondents surveyed in the region, 225 were from Hong Kong of whom most were aged 56 to 75 years, retired, and had no history of any previous prostate surgery. Overall, the self-reported prevalence of nocturia of at least one void per night was 93% (95% confidence interval, 90%-97%), slow stream 76% (71%-82%), post-micturition dribble 70% (64%-76%), and urgency 50% (43%-56%). Symptoms for which most respondents reported "some" or "a lot" of bother included: nocturia, defined as at least two voids per night (77%), and urgency and post-micturition dribble (73%). Only 39% to 54% of patients had previously received treatment but were not entirely satisfied with it. An understanding of their condition remained suboptimal.

CONCLUSIONS

In Hong Kong, nocturia emerged as the most prevalent and one of the most bothersome symptoms among men who sought urologist care for lower urinary tract symptoms. Compared with the non-Hong Kong population, Hong Kong respondents tended to be highly symptomatic and bothered. They were, however, less likely to have received treatment and were generally less satisfied with previous treatment.

Comparison of mean frequency and median frequency in evaluating muscle fiber type selection in varying gait speed across healthy young adult individuals

The preferential slow and fast twitches fiber involvement in varying gait speed has not been thoroughly investigated. Attempt to classify fiber type in changing speed should be closely investigated and scrutinized as the histochemical-related experiments are cumbersome and time consuming. In addressing this issue, electromyography (EMG) is utilized to extract the muscle fiber type features by altering the muscle fatigue indices, namely mean frequency (MNF) and median frequency (MDF). Recently, there are no universal indices to determine the muscle type. In this paper, the MNF and MDF are employed in discovering the muscle type variation as the speed changes. Besides drawing the potential of MNF and MDF in unveiling the muscle type, both the parameters are applied to investigate the muscles that are recruited and which muscle type are involved as the gait velocity changes. In this study, six healthy and young participants are recruited, whereby the EMG sensors are placed on twelve lower extremity muscles. The EMG signals are then processed via Matlab software to deduce MNF and MDF. The MNF and MDF are determined from every of the phase gait, namely stance and swing. From the results obtained, it reveals that the superiority of the MNF over the MDF in determining and interpreting the muscle recruitment in both gait phases as the speed increases. The MNF, moreover, is able to show an apparent difference in muscle type selection compared to MDF. Interestingly, it is discovered that as the speed increases from slow to fast, the MNF decreases, which indicates that more muscle fiber type I is recruited. Contrarily, the MNF increases as the speed intensity decreases, which indicates that the distribution of muscle type II is prominent.

Characterization of Predictive Behavior of a Retina by Mutual Information

Probing a bullfrog retina with spatially uniform light pulses of correlated stochastic intervals, we calculate the mutual information between the spiking output at the ganglion cells measured with multi-electrode array (MEA) and the interval of the stimulus at a time shift later. The time-integrated information from the output about the future stimulus is maximized when the mean interval of the stimulus is within the dynamic range of the well-established anticipative phenomena of omitted-stimulus responses for the retina. The peak position of the mutual information as a function of the time shift is typically negative considering the processing delay of the retina. However, the peak position can become positive for long enough correlation time of the stimulus when the pulse intervals are generated by a Hidden Markovian model (HMM). This is indicative of a predictive behavior of the retina which is possible only when the hidden variable of the HMM can be recovered from the history of the stimulus for a prediction of its future. We verify that stochastic intervals of the same mean, variance, and correlation time do not result in the same predictive behavior of the retina when they are generated by an Ornstein-Uhlenbeck (OU) process, which is strictly Markovian.

Microvasculature of the Mouse Cerebral Cortex Exhibits Increased Accumulation and Synthesis of Hyaluronan With Aging

The microvasculature of the aged brain is less dense and more vulnerable to dysfunction than that of the young brain. Brain microvasculature is supported by its surrounding extracellular matrix, which is comprised largely of hyaluronan (HA). HA is continually degraded into lower molecular weight forms that induce neuroinflammation. We examined HA associated with microvessels (MV) of the cerebral cortex of young (4 months), middle-aged (14 months), and aged (24-26 months) mice. We confirmed that the density of cortical MV decreased with age. Perivascular HA levels increased with age, but there was no age-associated change in HA molecular weight profile. MV isolated from aged cortex had more HA than MV from young cortex. Examination of mechanisms that might account for elevated HA levels with aging showed increased HA synthase 2 (HAS2) mRNA and protein in aged MV relative to young MV. In contrast, mRNAs for HA-degrading hyaluronidases or hyaladherins that mitigate HA degradation showed no changes with age. Corresponding to increased HAS2, aged MV synthesized significantly more HA (of all molecular weight classes) in vitro than young MV. We propose that increased HA synthesis and accumulation in brain MV contributes to neuroinflammation and reduced MV density and function in aging.

Crosstalk Between T Lymphocytes and Lung Fibroblasts: Generation of a Hyaluronan-Enriched Extracellular Matrix Adhesive for Monocytes

In immunity and inflammation, T cells are often associated with stromal mesenchymal cells such as fibroblasts. Hyaluronan and proteins that associate with hyaluronan such as versican and tumor necrosis factor-inducible gene-6 (TSG-6) are extracellular matrix (ECM) components that promote leukocyte adhesion, accumulation, and activation. However, the factors responsible for producing this specialized ECM and its impact on inflammatory events are not well understood. In this study, we explored the role of T cells in stimulating lung fibroblasts to produce an ECM that impacts monocyte adhesion. We found that CD3/CD28-activated human CD4+ T cells when co-cultured with human lung fibroblasts stimulated the expression of mRNA for hyaluronan synthase 2 (HAS2) and decreased the expression of hyaluronidase 2 (HYAL2). This led to an increase in the deposition of hyaluronan that formed cable-like structures within the ECM. Co-culturing activated T cells with fibroblasts also led to increased expression and accumulation of TSG-6. Surprisingly, addition of activated CD4+ T cells to the fibroblasts reduced the expression of mRNA for versican, and increased the expression of enzymes that degrade versican, such as ADAMTS4 and ADAMTS9 (a disintegrin and metalloproteinase with a thrombospondin type-1 motif) leading to a decrease in versican in the ECM of the co-cultures. Furthermore, addition of human monocytes to these co-cultures resulted in elevated monocyte adhesion to the cable-like structures in the ECM when compared to controls. These results illustrate the importance of crosstalk between T cells and fibroblasts in promoting the generation of a matrix that is adhesive for monocytes. J. Cell. Biochem. 118: 2118-2130, 2017. © 2016 Wiley Periodicals, Inc.