Heart-brain axis: Pushing the boundaries of cardiovascular molecular imaging

Despite decades of research, the heart-brain axis continues to challenge investigators seeking to unravel its complex pathobiology. Strong epidemiologic evidence supports a link by which insult or injury to one of the organs increases the risk of pathology in the other. The putative pathways have important differences between sexes and include alterations in autonomic function, metabolism, inflammation, and neurohormonal mechanisms that participate in crosstalk between the heart and brain and contribute to vascular changes, the development of shared risk factors, and oxidative stress. Recently, given its unique ability to characterize biological processes in multiple tissues simultaneously, molecular imaging has yielded important insights into the interplay of these organ systems under conditions of stress and disease. Yet, additional research is needed to probe further into the mechanisms underlying the heart-brain axis and to evaluate the impact of targeted interventions.

Emerging PET Tracers in Cardiac Molecular Imaging

¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-sodium fluoride (NaF) represent emerging PET tracers used to assess atherosclerosis-related inflammation and molecular calcification, respectively. By localizing to sites with high glucose utilization, FDG has been used to assess myocardial viability for decades, and its role in evaluating cardiac sarcoidosis has come to represent a major application. In addition to determining late-stage changes such as loss of perfusion or viability, by targeting mechanisms present in atherosclerosis, PET-based techniques have the ability to characterize atherogenesis in the early stages to guide intervention. Although it was once thought that FDG would be a reliable indicator of ongoing plaque formation, micro-calcification as portrayed by NaF-PET/CT appears to be a superior method of monitoring disease progression. PET imaging with NaF has the additional advantage of being able to determine abnormal uptake due to coronary artery disease, which is obscured by physiologic myocardial activity on FDG-PET/CT. In this review, we discuss the evolving roles of FDG, NaF, and other PET tracers in cardiac molecular imaging.

Single-Cell RNA Sequencing Reveals Smooth Muscle Cells Heterogeneity in Experimental Aortic Dissection

Purpose: This study aims to illustrate the cellular landscape in the aorta of experimental aortic dissection (AD) and elaborate on the smooth muscle cells (SMCs) heterogeneity and functions among various cell types.

Methods: Male Apolipoprotein deficient (ApoE−/−) mice at 28 weeks of age were infused with Ang II (2,500 ng/kg/min) to induce AD. Aortas from euthanized mice were harvested after 7 days for 10×Genomics single-cell RNA sequencing (scRNA-seq), followed by the identification of cell types and differentially expressed genes (DEGs). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was conducted.

Results: AD was successfully induced in ApoE−/− mice. scRNA-seq identified 15 cell clusters and nine cell types, including non-immune cells (endothelials, fibroblasts, and SMCs) and immune cells (B cells, natural killer T cell, macrophages, dendritic cells, neutrophils, and mast cells). The relative numbers of SMCs were remarkably changed, and seven core DEGs (ACTA2,IL6,CTGF,BGN,ITGA8,THBS1, and CDH5) were identified in SMCs. Moreover, we found SMCs can differentiate into 8 different subtypes through single-cell trajectory analysis.

Conclusion: scRNA-seq technology can successfully identify unique cell composition in experimental AD. To our knowledge, this is the first study that provided the complete cellular landscape in AD tissues from mice, seven core DEGs and eight subtypes of SMCs were identified, and the SMCs have evolution from matrix type to inflammatory type.

PET-Based Imaging with 18F-FDG and 18F-NaF to Assess Inflammation and Microcalcification in Atherosclerosis and Other Vascular and Thrombotic Disorders

Positron emission tomography (PET) imaging with ¹⁸F-fluorodeoxyglucose (FDG) represents a method of detecting and characterizing arterial wall inflammation, with potential applications in the early assessment of vascular disorders such as atherosclerosis. By portraying early-stage molecular changes, FDG-PET findings have previously been shown to correlate with atherosclerosis progression. In addition, recent studies have suggested that microcalcification revealed by ¹⁸F-sodium fluoride (NaF) may be more sensitive at detecting atherogenic changes compared to FDG-PET. In this review, we summarize the roles of FDG and NaF in the assessment of atherosclerosis and discuss the role of global assessment in quantification of the vascular disease burden. Furthermore, we will review the emerging applications of FDG-PET in various vascular disorders, including pulmonary embolism, as well as inflammatory and infectious vascular diseases.

Willed action and attention to the selection of action

Actions are said to be 'willed' if we consciously pay attention to their selection. It has been suggested that they are associated with activations in the dorsal prefrontal cortex (area 46). However, because previous experiments typically used a 'free selection' paradigm to examine this hypothesis, it is unclear whether the results reflected the attention to the selection of action or the freedom of choice allowed by the tasks. In this experiment, we minimized the difference of working memory demand across task conditions by using novel stimuli in each trial. We found that activation in the dorsal prefrontal cortex on a free selection task was not significantly different from that induced by another task that required attention to the selection of action, although the responses were externally specified. This suggests that the dorsal prefrontal cortex is in fact associated with attention to the selection of action, but does not play a unique role in the generation of internally initiated actions. However, the presupplementary motor area (pre-SMA) may subserve this function as activity in this region was found to be tightly associated with the free selection of responses.

The status of diabetes mellitus in primary care institution and restructured hospitals in Singapore

The Diabcare-Asia Singapore 1998 project was carried out using data from 22 centres collected on paper forms to provide an overview of diabetes management and metabolic control status in 1697 diabetic patients from both primary health care clinic (PHC) (67%) and restructured hospital (RH) (33%) settings. PHC patients were on average older than RH patients (61.3 +/- 11.2 years vs 51.5 +/- 17.7 years), and had a shorter duration of diagnosed diabetes (9.2 +/- 6.8 years vs 12.0 +/- 8.5 years). The mean body mass index (BMI) for PHC patients was 25.5 +/- 4.4 kg/m2 vs 24.5 +/- 4.2 kg/m2 for RH patients. Proportionately more PHC than RH patients were overweight (BMI >25 kg/m2) (49% vs 42%). Patients with type I diabetes constituted 3.5% of PHC vs 18.1% of the RH cohort. HbA1c information was available for 92.5% of RH vs 69% of PHC patients. HbA1c measurements were <1% above ULN in 50% of PHC vs 37% of RH patients, while FBG was >7.8 mmol/l in >61% of all patients. Proteinuria (>500 mg/24 hrs) was reported in 13% of PHC vs 26% of RH patients tested. Microalbuminuria (20-300 mg/l) was noted in 36% of 171 RH patients tested. Oral hypoglycaemic agents were used as sole therapy in 83.5% of PHC vs 43% of RH patients. Eye, feet, renal and severe late complications were more commonly reported by RH than PHC patients. There is a variation in the patient profiles and care between PHC and RH patients.

A window on the current status of diabetes mellitus in Singapore--the Diabcare-Singapore 1998 study

The Diabcare-Singapore project was carried out in 22 clinics (general hospitals, GH and primary healthcare centres, PHC) to provide an overview of diabetes management and metabolic control status. Data from 1697 diabetic patients were collected on paper forms and analysed centrally. Type 2 diabetes mellitus patients constituted 91.4% and type I patients constituted 8.1% of population. The proportion of type I patients was greater in GH (18.1%) vs PHC (3.4%). The mean age (+/- SD) was 58.1 +/- 14.4 years and mean duration of diabetes was 10.1 +/- 7.5 years. Mean body mass index (BMI) was 25.1 +/- 4.4 kg/m2 and more than half (53%) of patients were overweight (BMI >25 kg/m2). Mean HbA1c and FBG levels were 8.0 (1.9% and 9.1 +/- 3.1 mmol/l. A total of 51% of patients had HbA1c (1% above the Upper Limits of Normal (ULN). Fasting blood glucose (FBG) was >7.8 mmol/l in 61% of patients. The majority (70%) had satisfactory levels of fasting lipids (triglycerides, total cholesterol and HDL-cholesterol). Only 19.7% practised home blood glucose self-monitoring, while 99% reported receiving some diabetes education. Sixteen percent of patients had abnormal levels of protein (>500 mg/24 h) in the urine, 3% had elevated serum creatinine levels and 36% had microalbuminuria. Retinopathy (12%), cataract (16%) and neuropathy (12%) were commonly reported diabetic complications. The data revealed suboptimal glycaemic control in about half of patients studied.

Changes in activation of alcohol expectancies in memory in relation to changes in alcohol use after participation in an expectancy challenge program

Memory model-based expectancy studies have shed light on the process by which expectancies may influence drinking but have not related changes in expectancy activation to drinking changes. In the present study, 38 undergraduates completed a drinking measure and factor-based and memory model-based expectancy measures, before and after an expectancy challenge intervention designed to alter expectancies. Expectancies were mapped into memory network format with individual differences scaling and likely paths of activation were modeled with preference mapping. Results indicated that exposure to the expectancy challenge led to a change in likely activation of expectancies for men, but not for women. In the 30 days after the intervention, alcohol use among men decreased significantly but did not change among women. Therefore, changes in likely activation corresponded to changes in drinking. These findings support a memory model conceptualization of expectancy influence on drinking.

Dermal fibroblasts do not enhance the graft take rate of autologous, cultured keratinocyte suspension on full-thickness wounds in rats

Dermal fibroblasts are known to play an important role in wound healing. In this study, cultured autologous keratinocyte suspension was applied with fibrin glue to the full-thickness wounds in rats (N = 20). Histological analysis on day 14 showed regenerated epithelium in 10 wounds (50%). Keratinocytes were also premixed with allogeneic dermal fibroblasts in a ratio of 3:1 and 5:1 before application to other full-thickness wounds (N = 20) with fibrin glue. Regeneration of epithelium was observed in 10 (50%) and 9 (45%) wounds respectively. Acute inflammatory reaction and mild to moderate proliferation of fibroblasts in the subepithelial layer of the allogeneic fibroblasts were noted. The addition of dermal fibroblasts to keratinocytes/fibrin glue does not enhance the take rate of the cultured keratinocyte suspension.

A new technique to resurface wounds with composite biocompatible epidermal graft and artificial skin

BACKGROUND

The incorporation of cultured epidermal autograft on the neodermis of artificial skin (Integra, Integra LifeSciences, Plainsboro, NJ) has been met with some difficulties. A new engraftment technique to resurface the wounds with Integra and composite biocompatible epidermal graft (CBEG) has been successfully applied on three patients for elective reconstructive procedures.

METHODS

A small skin biopsy was taken from the normal edge of the lesion for keratinocytes and dermal fibroblast cultures 2 weeks before surgery. When sufficient cells were grown, the patient was admitted for the excision of the lesions or scars. The wounds of the patients, ranging from 125 to 250 cm2, were covered with Integra. When the neodermis of the Integra was fully vascularized, the silicone membrane of the Integra was removed and replaced with the CBEG, which consisted of autologous keratinocytes cultivated on a hyaluronate-derived membrane (Laserskin; Fidia Advanced Biopolymers, Abano Terme, Italy)) using human dermal fibroblasts as a feeder layer.

RESULTS

Clinically, there was good initial "take" of the CBEGs in these three patients, ranging from 50% to 100%. Biopsy specimens of the grafted wounds were taken 1 to 3 weeks after the application of the CBEGs. Epithelialization was noted in all patients.

CONCLUSION

This engraftment technique has several advantages. The CBEG is much easier to handle than the conventional cultured epidermal autograft. It eliminates the invasive second procedure for skin harvesting, with resulting pain and scarring. The application of the CBEG can be easily performed at the bedside.

Changes in activation of alcohol expectancies in memory in relation to changes in alcohol use after participation in an expectancy challenge program

Memory model-based expectancy studies have shed light on the process by which expectancies may influence drinking but have not related changes in expectancy activation to drinking changes. In the present study, 38 undergraduates completed a drinking measure and factor-based and memory model-based expectancy measures, before and after an expectancy challenge intervention designed to alter expectancies. Expectancies were mapped into memory network format with individual differences scaling and likely paths of activation were modeled with preference mapping. Results indicated that exposure to the expectancy challenge led to a change in likely activation of expectancies for men, but not for women. In the 30 days after the intervention, alcohol use among men decreased significantly but did not change among women. Therefore, changes in likely activation corresponded to changes in drinking. These findings support a memory model conceptualization of expectancy influence on drinking.

A new system for the cultivation of keratinocytes on acellular human dermis with the use of fibrin glue and 3T3 feeder cells

The growth of human keratinocytes on human acellular dermis in 4 different culture systems was compared. Epidermis was completely separated and removed from dermis after skin samples had been soaked in 0.1% trypsin at 4 degrees C for 1 week. Forty pieces of saline-washed dermis, 1 cm2 each, were randomized into 4 groups: in group A, human keratinocytes that had undergone 2 to 3 cell passages were seeded (30 x 10(4) cell/cm2) onto the dermis and sprayed with a thin layer of fibrin glue and proliferative 3T3 feeder cells that had been growing separately on the culture dish; in group B, the dermis was only sprayed with fibrin glue; in group C, the dermis was treated with 3T3 cells only; and in group D, the dermis was not sprayed with anything. The dermis samples in all groups were raised on a grid to provide an air-liquid culture system. Histology results of the composite grafts at 2 weeks were assessed as having either scanty colonies of keratinocytes (SCK), continuous stratified epithelium (CSE), or no observable keratinocyte growth. Eight out of the ten dermis samples (80%) in group A demonstrated CSE, and 30% of the samples in group B showed SCK. There were 10% SCK and 20% CSE in group C, and in group D, 30% SCK and 10% CSE were found. The good results in group A indicated that the fibrin glue facilitated the seeding efficiency of the keratinocytes on the dermis and that the vital factors released from the 3T3 feeder cells enhanced the growth and differentiation of the keratinocytes. This model provides an optimal system for the cultivation of keratinocytes on acellular dermis.

Mass screening for diabetic retinopathy--a report on diabetic retinal screening in primary care clinics in Singapore

INTRODUCTION

Mass screening for diabetic retinopathy is expensive and inaccessible if done by institutional ophthalmalogists. Most diabetics are seen in primary care. Hence it is logical to provide mass screening in primary care clinics. In Singapore, government polyclinics are ideal centres of screening as they are well organised and accessible to the community. SCREENING METHOD: An effective mass screening strategy must provide wide coverage, be low cost and have the ability to assess diabetic eyes accurately and quickly. Non-mydriatic fundal photography was used as the screening method. Mass coverage was achieved by rotating two cameras around six government polyclinics. Cost was reduced by training existing staff and organising the programme to provide a high turnover of screenees. The photographs were read by ophthalmologists in a government-owned hospital. Patients that required referral were referred to specialist eye clinics.

RESULTS

A total of 13,296 patients were screened or rescreened during a period of 2 years (25 months). 2,911 patients or 21.8% of the total screened were found to have diabetic retinopathy. About half of these (10.8%) had sight threatening retinopathy. The most common sight threatening retinopathy was maculopathy (8.0%). Twenty-two percent of cases screened were referred. These include referral for other ocular conditions detected during the screening.

CONCLUSION

Non-mydriatic fundal photography has proven to be both accessible and effective in screening diabetic eyes in urban Singapore and can be recommended for mass screening of diabetic eyes in the community.

Wound care in the elderly patient

Wound care in the elderly population requires careful attention to the medical status of the patient. The patient's underlying medical condition can often dictate what reconstructive options are appropriate. Many reconstructive techniques are available to repair a wide variety of wounds.

Results of surgical treatment of talipes equinovarus congenita

A series of 153 feet in 103 patients were surgically treated for idiopathic clubfeet (mean follow-up period of 10.3 years). Thirty-four percent had prior surgery before referral to the authors' institution. Functional results were excellent in 28.7%, good in 37.9%, fair in 13.1%, and unsatisfactory in 20.3%. The complication rate was 7.4%. Serious complications included translocation of os calcis, avascular necrosis of the talus, and injuries to neurovascular structures. Pain after strenuous activities was noted in 11.3% of the feet. In 9.8% of feet, limitation of activities was noted by the patients. Translocation of the hindfoot was associated with extensive subtalar release and often resulted in poor function. At operation, extensive subtalar release should only be performed with caution after failure of correction from release of other medial and posterior structures.

Body weight and depot fat changes as influenced by exercise and dietary fat sources in adult BHE rats

Adult male BHE rats were fed diets containing 15% of either corn oil (CO) or medium chain triglycerides (MCT) as the dietary source of fat. Further, rats were allowed to remain sedentary or were forced to exercise by swimming for 1 hour daily, for 3 weeks, followed by swimming for 2 hours daily for 3 weeks. The exercise for 3 weeks caused significant reductions in average body weight gains. After 6 weeks of exercise the lipid content of the adipose cells was reduced by about 50%. Fat cell numbers were not changed by either fat source or exercise, but fat cell size was significantly reduced after swimming daily for 6 weeks.

Prenatal development of acid beta-glycosidases in the rat liver, effect of triiodothyronine or cortisone administered to pregnant rats

We have found that acid beta-galactosidase, beta-glucuronidase and N-acetyl-beta-glucosaminidase in the rat fetal liver increase during the last week of pregnancy. These enzyme activities were influenced by treatment of pregnant rats (daily from day 16) with L-tri-iodothyronine (20 or 50 microgram/100 gm b.w.) or cortisone acetate (10 or 50 mg/100 gm b.w.) as studied in their fetuses obtained on day 22 by caesarian section.

Effect of cortisone or triiodothyronine administration to pregnant rats on lysosomal hydrolases in fetal forebrain and cerebellum

Triiodothyronine injected daily to pregnant rats for the last week of gestation (50 microgram/100 g b.wt) increased the specific activities of 5 acid glycosidases in the fetal forebrain and cerebellum. Cortisone (50 mg/100 g b.wt) administered in the same period had no effect on cerebellum acid hydrolases, but decreased their activity in the forebrain.

Comparison of postnatal development of several acid glycosidases in the rat forebrain and cerebellum

Changes of activity of several glycosidases (beta-galactosidase, beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, alpha-D-mannosidase and alpha-L-fucosidase) were compared in the forebrain and cerebellum during postnatal development of the rat. Detailed analysis of the data showed similarities, but also substantial differences in their development in both organs. This is interpreted as an indication of the presence of common regulatory mechanisms, as well as of other factors which differently influence development of the glycosidases studied in both CNS parts.