Healthy biological systems exhibit complex patterns of variability that can be described by mathematical chaos. Heart rate variability (HRV) consists of changes in the time intervals between consecutive heartbeats called interbeat intervals (IBIs). A healthy heart is not a metronome. The oscillations of a healthy heart are complex and constantly changing, which allow the cardiovascular system to rapidly adjust to sudden physical and psychological challenges to homeostasis. This article briefly reviews current perspectives on the mechanisms that generate 24 h, short-term (~5 min), and ultra-short-term (<5 min) HRV, the importance of HRV, and its implications for health and performance. The authors provide an overview of widely-used HRV time-domain, frequency-domain, and non-linear metrics. Time-domain indices quantify the amount of HRV observed during monitoring periods that may range from ~2 min to 24 h. Frequency-domain values calculate the absolute or relative amount of signal energy within component bands. Non-linear measurements quantify the unpredictability and complexity of a series of IBIs. The authors survey published normative values for clinical, healthy, and optimal performance populations. They stress the importance of measurement context, including recording period length, subject age, and sex, on baseline HRV values. They caution that 24 h, short-term, and ultra-short-term normative values are not interchangeable. They encourage professionals to supplement published norms with findings from their own specialized populations. Finally, the authors provide an overview of HRV assessment strategies for clinical and optimal performance interventions.

/pdf/an-overview-of-heart-rate-variability-metrics-and-norms-sd8bxpnvjg.pdf

An Overview of Heart Rate Variability Metrics and Norms.

In addition to being a public physical health emergency, Coronavirus disease 2019 (COVID-19) affected global mental health, as evidenced by panic-buying worldwide as cases soared. Little is known about changes in levels of psychological impact, stress, anxiety and depression during this pandemic. This longitudinal study surveyed the general population twice - during the initial outbreak, and the epidemic's peak four weeks later, surveying demographics, symptoms, knowledge, concerns, and precautionary measures against COVID-19. There were 1738 respondents from 190 Chinese cities (1210 first-survey respondents, 861 s-survey respondents; 333 respondents participated in both). Psychological impact and mental health status were assessed by the Impact of Event Scale-Revised (IES-R) and the Depression, Anxiety and Stress Scale (DASS-21), respectively. IES-R measures PTSD symptoms in survivorship after an event. DASS -21 is based on tripartite model of psychopathology that comprise a general distress construct with distinct characteristics. This study found that there was a statistically significant longitudinal reduction in mean IES-R scores (from 32.98 to 30.76, p  24) for PTSD symptoms, suggesting that the reduction in scores was not clinically significant. During the initial evaluation, moderate-to-severe stress, anxiety and depression were noted in 8.1%, 28.8% and 16.5%, respectively and there were no significant longitudinal changes in stress, anxiety and depression levels (p > 0.05). Protective factors included high level of confidence in doctors, perceived survival likelihood and low risk of contracting COVID-19, satisfaction with health information, personal precautionary measures. As countries around the world brace for an escalation in cases, Governments should focus on effective methods of disseminating unbiased COVID-19 knowledge, teaching correct containment methods, ensuring availability of essential services/commodities, and providing sufficient financial support.

A longitudinal study on the mental health of general population during the COVID-19 epidemic in China.

Context Anemia is a common problem in critically ill patients admitted to intensive care units (ICUs), but the consequences of anemia on morbidity and mortality in the. critically ill is poorly defined. Objectives To prospectively define the incidence of anemia and use of red blood cell (RBC) transfusions in critically ill patients and to explore the potential benefits and risks associated with transfusion in the ICU. Design Prospective observational study conducted November 1999, with 2. components: a blood sampling study and an, anemia and blood transfusion study. Setting and Patients The blood sampling study included 1136 patients from 145 western European ICUs, and the anemia and blood transfusion study included 3534 patients from 146 western European ICUs. Patients were followed up for 28 days or until hospital discharge, interinstitutional transfer, or death. Main Outcome Measures Frequency of blood drawing and associated volume of blood drawn, collected over a 24-hour period; hemoglobin levels, transfusion rate, organ dysfunction (assessed using the Sequential Organ Failure Assessment score), and mortality, collected throughout a 2-week period. Results The mean (SD) volume per blood draw was 10.3 (6.6) mL, with an average total volume of 41.1 (39.7) mL during the 24-hour period. There was a positive correlation between organ dysfunction and the number of blood draws (r=0.34; P<.001) and total volume drawn (r=0.28; P<.001). The mean hemoglobin concentration at ICU admission was 11.3 (2.3) g/dL, with 29% (963/3295) having a concentration of less than 10 g/dL. The transfusion rate during the ICU period was 37.0% (1307/3534). Older patients and those with a longer ICU length of stay were more commonly transfused. Both ICU and overall mortality rates were significantly higher in patients who had vs had not received a transfusion (ICU rates: 18.5% vs 10.1%, respectively; chi(2)=50.1; P<.001; overall rates: 29.0% vs 14.9%, respectively; chi(2) =88.1; P<.001). For similar degrees of organ dysfunction, patients who had a transfusion had a higher mortality rate. For matched patients in the propensity analysis, the 28-day mortality was 22.7% among patients with transfusions and 17.1% among those without (P=.02); the Kaplan-Meier log-rank test confirmed this difference. Conclusions This multicenter observational study reveals the common occurrence of anemia and the large use of blood transfusion in critically ill patients. Additionally, this epidemiologic study provides evidence of an association between transfusions and diminished organ function as well as between transfusions and mortality.

https://jamanetwork.com/journals/jama/articlepdf/195310/jce10054.pdf

Anemia and blood transfusion in critically ill patients.

Treatment of acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), remain unsolved problems of intensive care medicine. ALI/ARDS are characterized by lung edema due to increased permeability of the alveolar-capillary barrier and subsequent impairment of arterial oxygenation. Lung edema, endothelial and epithelial injury are accompanied by an influx of neutrophils into the interstitium and broncheoalveolar space. Hence, activation and recruitment of neutrophils are regarded to play a key role in progression of ALI/ARDS. Neutrophils are the first cells to be recruited to the site of inflammation and have a potent antimicrobial armour that includes oxidants, proteinases and cationic peptides. Under pathological circumstances, however, unregulated release of these microbicidal compounds into the extracellular space paradoxically can damage host tissues. This review focuses on the mechanisms of neutrophil recruitment into the lung and on the contribution of neutrophils to tissue damage in ALI.

Contribution of neutrophils to acute lung injury.

The membrane transferrin receptor-mediated endocytosis or internalization of the complex of transferrin bound iron and the transferrin receptor is the major route of cellular iron uptake. This efficient cellular uptake pathway has been exploited for the site-specific delivery not only of anticancer drugs and proteins, but also of therapeutic genes into proliferating malignant cells that overexpress the transferrin receptors. This is achieved either chemically by conjugation of transferrin with therapeutic drugs, proteins, or genetically by infusion of therapeutic peptides or proteins into the structure of transferrin. The resulting conjugates significantly improve the cytotoxicity and selectivity of the drugs. The coupling of DNA to transferrin via a polycation or liposome serves as a potential alternative to viral vector for gene therapy. Moreover, the OX26 monoclonal antibody against the rat transferrin receptor offers great promise in the delivery of therapeutic agents across the blood-brain barrier to the brain.

Targeted Drug Delivery via the Transferrin Receptor-Mediated Endocytosis Pathway

Lactoferrin is a 703-amino acid glycoprotein originally isolated from milk Plasma lactoferrin is predominantly neutrophil derived but indications are that it may also be produced by other cells Lactoferrin in body fluids is found in the iron-free form, the monoferric form and in the diferric form Three isoforms of lactoferrin have been isolated, ie two with RNase activity (lactoferrin-beta and lactoferrin-gamma) and one without RNase activity (lactoferrin-alpha) Receptors for lactoferrin can be found on intestinal tissue, monocytes/macrophages, neutrophils, lymphocytes, platelets, and on certain bacteria A wide spectrum of functions are ascribed to lactoferrin These range from a role in the control of iron availability to immune modulation More research is necessary however to obtain clarity with regard to the exact mechanism of action of lactoferrin

Lactoferrin: a general review

Ferritin is the intracellular protein responsible for the sequestration, storage and release of iron. Ferritin can accumulate up to 4500 iron atoms as a ferrihydrite mineral in a protein shell and releases these iron atoms when there is an increase in the cell's need for bioavailable iron. The ferritin protein shell consists of 24 protein subunits of two types, the H-subunit and the L-subunit. These ferritin subunits perform different functions in the mineralization process of iron. The ferritin protein shell can exist as various combinations of these two subunit types, giving rise to heteropolymers or isoferritins. Isoferritins are functionally distinct and characteristic populations of isoferritins are found depending on the type of cell, the proliferation status of the cell and the presence of disease. The synthesis of ferritin is regulated both transcriptionally and translationally. Translation of ferritin subunit mRNA is increased or decreased, depending on the labile iron pool and is controlled by an iron-responsive element present in the 5'-untranslated region of the ferritin subunit mRNA. The transcription of the genes for the ferritin subunits is controlled by hormones and cytokines, which can result in a change in the pool of translatable mRNA. The levels of intracellular ferritin are determined by the balance between synthesis and degradation. Degradation of ferritin in the cytosol results in complete release of iron, while degradation in secondary lysosomes results in the formation of haemosiderin and protection against iron toxicity. The majority of ferritin is found in the cytosol. However, ferritin with slightly different properties can also be found in organelles such as nuclei and mitochondria. Most of the ferritin produced intracellularly is harnessed for the regulation of iron bioavailability; however, some of the ferritin is secreted and internalized by other cells. In addition to the regulation of iron bioavailability ferritin may contribute to the control of myelopoiesis and immunological responses.

/pdf/ferritin-and-ferritin-isoforms-i-structure-function-1yo68kcboi.pdf

Ferritin and ferritin isoforms I: Structure–function relationships, synthesis, degradation and secretion

The validity of melatonin as a prominent, naturally occurring oncostatic agent is examined in terms of its putative oncostatic mechanism of action, the correlation between melatonin levels and neoplastic activity, and the outcome of therapeutically administered melatonin in clinical trials. Melatonin's mechanism of action is summarized in a brief analysis of its actions at the cellular level, its antioxidative functions, and its indirect immunostimulatory effects. The difficulties of interpreting melatonin levels as a diagnostic or prognostic aid in cancer is illustrated by referral to breast cancer, the most frequently studied neoplasm in trials regarding melatonin. Trials in which melatonin was used therapeutically are reviewed, i.e., early studies using melatonin alone, trials of melatonin in combination with interleukin-2, and controlled studies comparing routine therapy to therapy in combination with melatonin. A table compiling the studies in which melatonin was used in the treatment of cancer in humans is presented according to the type of neoplasm. Melatonin's suitability in combination chemotherapy, where it augments the anticancer effect of other chemotherapeutic drugs while decreasing some of the toxic side effects, is described. Based on the evidence derived from melatonin's antiproliferative, antioxidative, and immunostimulatory mechanisms of action, from its abnormal levels in cancer patients and from clinical trials in which melatonin was administered, it is concluded that melatonin could indeed be considered a physiological anticancer substance. Further well-controlled trials should, however, be performed in order to find the link between its observed effects and the underlying mechanisms of action and to define its significance as a therapeutic oncostatic agent.

The validity of melatonin as an oncostatic agent.

Overweight and obesity in children and adolescents are on the increase worldwide.Overweight and obesity increase the risk for the development of non-communicable diseases during childhood and adolescence, and predispose the individual to the development of overweight, obesity,ardiovascular disease, and metabolic and other disorders in adulthood.In Africa the number of overweight or obese children has doubled since 1990. In South Africa,overweight and obesity in children and adolescents are on the increase, but the prevalencevaries with age, gender and population group. These differences are important when intervention programmes and policies are considered. South Africa faces a double burden of disease where undernutrition and overweight or obesity are found in the same populations, in the same households and even in the same children. Malnutrition is a major contributor to the double burden of disease in South African children and adolescents.

/pdf/overweight-and-obesity-in-children-and-adolescents-the-south-57cyfd1xxj.pdf

Margaretha Viljoen

Papers

Lactoferrin: a general review

Ferritin and ferritin isoforms I: Structure–function relationships, synthesis, degradation and secretion

The validity of melatonin as an oncostatic agent.

Overweight and obesity in children and adolescents: The South African problem

Physicians' difficulty with emergency department patients is related to patients' attachment style.